HEALTHCARE COST AND UTLIZATION PROJECT HCUP
A FEDERAL-STATE-INDUSTRY PARTNERSHIP IN HEALTH DATA
Sponsored by the Agency for Healthcare Research and Quality
THE HCUP KIDS' INPATIENT DATABASE (KID),
|These pages provide only an introduction to the KID package.|
For full documentation and notification of changes, visit the HCUP User Support (HCUP-US) website at http://www.hcup-us.ahrq.gov.
Issued June 2008
Updated November 2015
Agency for Healthcare Research and Quality
Healthcare Cost and Utilization Project (HCUP)
KID Data and Documentation Distributed by:
HCUP Central Distributor
Phone: (866) 290-HCUP (4287)
Fax: (866) 792-5313
Table of ContentsSkip Table of Contents
- SUMMARY OF DATA USE LIMITATIONS
- HCUP CONTACT INFORMATION
- WHAT’S NEW IN THE 2006 KIDS' INPATIENT DATABASE (KID)?
- UNDERSTANDING THE KID
- INTRODUCTION TO THE HCUP KIDS' INPATIENT DATABASE (KID)
- Overview of KID Data
- Getting Started
- HOW TO USE THE KID FOR DATA ANALYSIS
- SAMPLING OF DISCHARGES
- Sampling of Discharges Included in the KID
- Hospital Sampling Frame
- Hospital Sample Design
- SAMPLE WEIGHTS
- THE FINAL KID SAMPLE
- APPENDIX I: TABLES AND FIGURES
- Table 1. Data Sources
- Table 2. Summary of KID Data Sources, Hospitals, and Inpatient Stays, 1997, 2000, 2003, and 2006
- Figure 1. KID States, by Region
- Table 3. Summary of KID Releases
- Table 4. KID Related Reports and Database Documentation Available on HCUP-US
- Table 5. States, by Region
- Table 6. Bed Size Categories, by Region
- Table 7. Number of AHA, HCUP SID, and KID Hospitals, by State, 2006
- Table 8. Number of Hospitals and Discharges in the AHA Universe, SID, and KID, by Hospital Type, 2006
- Table 9. 2006 KID Discharges, by Hospital Type
- Figure 2. Number of Hospitals in the 2006 AHA Universe, SID, and KID, by Region
- Figure 3. Percentage of U.S. Population in 2006 KID States, by Region
- Figure 4. Number of Discharges in the 2006 KID, by State
- APPENDIX II: STATE-SPECIFIC RESTRICTIONS
- APPENDIX III: DATA ELEMENTS
HCUP KIDS' INPATIENT DATABASE (KID) SUMMARY OF DATA USE LIMITATIONS
***** REMINDER *****
All users of the KID must take the on-line HCUP Data Use Agreement (DUA) training course, and read and sign a Data Use Agreement.†
Authorized users of HCUP data agree to the following limitations: ‡
Any violation of the limitations in the Data Use Agreement is punishable under Federal law by a fine of up to $10,000 and up to 5 years in prison. Violations may also be subject to penalties under State statutes.
† The on-line Data Use Agreement training session and the Data Use Agreement are available on the HCUP User Support ( HCUP-US) website at http://www.hcup-us.ahrq.gov.
HCUP CONTACT INFORMATION
All HCUP data users, including data purchasers and collaborators, must complete the online HCUP Data Use Agreement (DUA) Training Tool, and read and sign the HCUP Data Use Agreement. Proof of training completion and signed Data Use Agreements must be submitted to the HCUP Central Distributor as described below.
The on-line DUA training course is available at: http://www.hcup-us.ahrq.gov/tech_assist/dua.jsp.
The HCUP Nationwide Data Use Agreement are is available on the AHRQ-sponsored HCUP User Support (HCUP-US) website at:
HCUP Central Distributor
Data purchasers will be required to provide their DUA training completion code and will execute their DUAs electronically as a part of the online ordering process. The DUAs and training certificates for collaborators and others with access to HCUP data should be submitted directly to the HCUP Central Distributor using the contact information below.
The HCUP Central Distributor can also help with questions concerning HCUP database purchases, your current order, training certificate codes, or invoices, if your questions are not covered in the Purchasing FAQs on the HCUP Central Distributor website.
Phone: 866-556-HCUP (4287) (toll free)
Fax: 866-792-5313 (toll free in the United States)
HCUP Central Distributor
Social & Scientific Systems, Inc.
8757 Georgia Ave, 12th Floor
Silver Spring, MD 20910
HCUP User Support:
Information about the content of the HCUP databases is available on the HCUP User Support (HCUP-US) website (http://www.hcup-us.ahrq.gov). If you have questions about using the HCUP databases, software tools, supplemental files, and other HCUP products, please review the HCUP Frequently Asked Questions or contact HCUP User Support:
WHAT’S NEW IN THE 2006 KIDS' INPATIENT DATABASE (KID)?
UNDERSTANDING THE KID
HEALTHCARE COST AND UTILIZATION PROJECT HCUP
A FEDERAL-STATE-INDUSTRY PARTNERSHIP IN HEALTH DATA
Sponsored by the Agency for Healthcare Research and Quality
The Agency for Healthcare Research and Quality and
the staff of the Healthcare Cost and Utilization Project (HCUP) thank you for
purchasing the HCUP Kids' Inpatient Database (KID).
HCUP Kids' Inpatient Database (KID)
The Kids’ Inpatient Database (KID) is part of the Healthcare Cost and Utilization Project (HCUP), sponsored by the Agency for Healthcare Research and Quality (AHRQ), formerly the Agency for Health Care Policy and Research.
The KID is the only dataset on hospital use, outcomes, and charges designed to study children’s use of hospital services in the United States. The KID is a sample of discharges from all community, non-rehabilitation hospitals in States participating in HCUP. The target universe includes pediatric discharges from community, non-rehabilitation hospitals in the United States. Pediatric discharges are defined as all discharges where the patient was age 20 or less at admission. See Table 1 in Appendix I for a list of the statewide data organizations participating in the KID. The number of sample hospitals and discharges by State and year are available in Table 2 in Appendix I.
The KID contains charge information on all patients, regardless of payer, including persons covered by private insurance, Medicaid, Medicare, and the uninsured. The KID's large sample size enables analyses of rare conditions, such as congenital anomalies and uncommon treatments, such as organ transplantation. It can be used to study a wide range of topics including the economic burden of pediatric conditions, access to services, quality of care and patient safety, and the impact of health policy changes.
Inpatient stay records in the KID include clinical and resource use information typically available from discharge abstracts. Discharge weights are provided for calculating national estimates. The KID can be linked to hospital-level data from the American Hospital Association's Annual Survey Database (Health Forum, LLC © 2012) and county-level data from the Bureau of Health Professions' Area Resource File, except in those States that do not allow the release of hospital identifiers.
The KID is available every three years beginning with 1997. Periodically, new data elements are added to the KID and some are dropped; see Appendix III for a summary of data elements and when they are effective.
Access to the KID is open to users who sign Data Use Agreements. Uses are limited to research and aggregate statistical reporting.
For more information on the KID, visit the AHRQ-sponsored HCUP User Support (HCUP-US) Website at http://www.hcup-us.ahrq.gov.
INTRODUCTION TO THE HCUP KIDS’ INPATIENT DATABASE (KID)
Overview of KID Data
The Healthcare Cost and Utilization Project (HCUP) Kids’ Inpatient Database (KID) was developed to enable analyses of hospital utilization by children across the United States. The target universe includes pediatric discharges from community, non-rehabilitation hospitals in the United States.1
Pediatric discharges are defined as all discharges where a patient was 20 years or less at admission. Discharges with missing, invalid, or inconsistent ages are excluded. Pediatric discharges are identified as one of three types of records:
- Uncomplicated in-hospital births (HOSPBRTH = 1 and UNCBRTH = 1)
- Complicated in-hospital births (HOSPBRTH = 1 and UNCBRTH = 0)
- All other pediatric cases (HOSPBRTH = 0).
In-hospital births (HOSPBRTH = 1) are identified by any principal or secondary diagnosis code in the range of V3000 to V3901 with the last two digits of "00" or "01" and the patient is not transferred from another acute care hospital or healthcare facility. Uncomplicated births (UNCBRTH = 1) have a Diagnosis Related Group (DRG) equal to 391 indicating "Normal Newborn."
Unlike the HCUP Nationwide Inpatient Sample (NIS), the KID does not involve a two-stage sampling procedure. Instead, the KID includes a sample of pediatric discharges from all hospitals in the sampling frame – the State Inpatient Databases (SID) that agreed to participate in the KID). For sampling, pediatric discharges are stratified by uncomplicated in-hospital birth, complicated in-hospital birth, and all other pediatric cases. To further ensure an accurate representation of each hospital's pediatric case-mix, the discharges are sorted by State, hospital, DRG, and a random number within each DRG. Systematic random sampling is used to select 10% of uncomplicated in-hospital births and 80% of complicated in-hospital births and other pediatric cases from each frame hospital.
To obtain national estimates, discharge weights are developed using the AHA universe as the standard. For the weights, hospitals are post-stratified on six characteristics contained in the AHA hospital files. These were the same characteristics used to define the NIS sampling strata (ownership/control, bedsize, teaching status, rural/urban location, and U.S. region), with the addition of a stratum for freestanding children’s hospitals. To create weights, if there were fewer than two frame hospitals, 30 uncomplicated births, 30 complicated births, and 30 non-birth pediatric discharges sampled in a stratum, that stratum is combined with an "adjacent" stratum containing hospitals with similar characteristics. Discharge weights are created by stratum in proportion to the number of AHA newborns for newborn discharges and in proportion to the total number of (non-newborn) AHA discharges for non-newborn discharges.
Detailed information on the design of the KID prior to 2006 is available in the year-specific special reports on Design of the Kids’ Inpatient Database found on the HCUP-US Website (http://hcup-us.ahrq.gov/db/nation/kid/kidrelatedreports.jsp). Starting with the 2006 KID, the information on the design of the KID was incorporated into this report, which describes the KID sample and weights, summarizes the contents of the 2006 KID, and discusses data analysis issues. This document highlights cumulative information for all previous KID releases to provide a longitudinal view of the database. We have enhanced the nationwide representation of the sample by incorporating data from additional HCUP State Partners.
- Data in fixed-width ASCII format on CD-ROM.
- 2 million to 3 million pediatric inpatient records per year.
- 2,500 to 3,500 hospitals per year (all SID hospitals with pediatric discharges).
- Discharge-level weights to calculate national estimates for discharges.
- Hospital File to link the KID to data from the AHA Annual Survey Database.
- KID Documentation and tools – including file specifications, programming source code for loading ASCII data into SAS and SPSS, and value labels. Beginning in 2006, code is also provided for loading the KID ASCII file into STATA.
KID Data Sources, Hospitals, and Inpatient Stays
Table 2 in Appendix I contains a summary of the data sources, number of hospitals, and number of inpatient stays in each KID database. It also lists the differences in types of hospitals and age inclusion for pediatric cases.
Some data sources that contributed data to the KID imposed restrictions on the release of certain data elements or on the number and types of hospitals that could be included in the database. Because of confidentiality laws, some data sources were prohibited from providing HCUP with discharge records that indicated specific medical conditions, such as HIV/AIDS or behavioral health. Detailed information on these State-specific restrictions is available in Appendix II.
Contents of CD-ROM
The KID is contained on one CD-ROM that include fixed-width ASCII formatted data files and a README.TXT file describing how to access related KID documentation on the HCUP-US Website (http://www.hcup-us.ahrq.gov).
The CD-ROM contains:
Inpatient Core File: The Core file contains pediatric discharges sampled from community, non-rehabilitation hospitals in participating HCUP States. The unit of observation is an inpatient stay record. The Core file contains data elements for linkage, patient demographics, clinical information, and payment information. Sample weights for the three types of records, uncomplicated in-hospital births, complicated in-hospital births, and all other pediatric cases, are calculated separately by stratum and are added to each discharge in the Core File, as appropriate, so that only one discharge weight variable (DISCWT) is needed. See Table 1 of Appendix III for a list of data elements in the Inpatient Core File. This file is available in all years of the KID.
Hospital File: The hospital-level file contains one observation for each hospital included in the KID and contains variance estimation data elements, linkage data elements, and data elements that describe basic characteristics about hospitals. The unit of observation is the hospital. The HCUP hospital identifier (HOSPID) provides the linkage between the KID Inpatient Core file and the Hospital file. See Table 2 of Appendix III for a list of data elements in the Hospital File. This file is available in all years of the KID.
Disease Severity Measures File: This discharge-level file contains information from four different sets of disease severity measures. Information from the severity file is to be used in conjunction with the inpatient Core file. The unit of observation is an inpatient stay record. The HCUP unique record identifier (RECNUM) provides the linkage between the Core file and the Disease Severity Measures files. See Appendix III, Table 3 for a list of data elements in the Severity Measures Files. This file is available beginning with the 2003 KID.
Diagnosis and Procedure Groups Files: These discharge-level files contain data elements from AHRQ software tools designed to facilitate the use of the ICD-9-CM diagnostic and procedure information in the HCUP databases. The unit of observation is an inpatient stay record. The HCUP unique record identifier (KEY) provides the linkage between the Core files and the Diagnosis and Procedure Groups files. Table 4 in Appendix III contains a list of data elements in the Diagnosis and Procedure Groups files. These files are available beginning with the 2006 KID.
On the HCUP-US Website (http://www.hcup-us.ahrq.gov), KID purchasers can access complete file documentation, including variable notes, file layouts, summary statistics, and related technical reports. Similarly, purchasers can also download SAS, SPSS, and STATA load programs. Available online documentation and supporting files are detailed in Appendix I, Table 4.
KID Data Elements
The KID contains two types of data: inpatient stay core records and hospital information. Appendix III identifies the data elements in each KID file:
- Table 1 for the Inpatient Core files (record = inpatient stay)
- Table 2 for the Hospital Weights files (record = hospital)
- Table 3 for the Disease Severity Measures files (record = inpatient stay). This file was added beginning with the 2003 KID.
- Table 4 for the Diagnosis and Procedure Groups files (record = inpatient stay). This file was added beginning with the 2006 KID.
Not all data elements in the KID are uniformly coded or available across all States. The tables in Appendix III are not complete documentation for the data. Please refer to the KID documentation located on the HCUP-US Website (http://hcup-us.ahrq.gov) for comprehensive information about data elements and the files.
The KID data files are provided on one CD-ROM. Comprehensive documentation for the KID files is available on the HCUP-US Website (http://hcup-us.ahrq.gov).
KID Data Files
In order to load KID data onto your PC, you will need about five gigabytes of space available. Because of the size of the files, the data are distributed as self-extracting PKZIP compressed files. To decompress the data, you should follow these steps:
- Create a directory for the KID on your hard drive.
- Copy the self-extracting data files from the KID Data Files CD-ROM into the new directory.
- Unzip each file by running the corresponding *.exe file.
- Type the file name within DOS or click on the name within Windows Explorer.
- Edit the name of the "Unzip To Folder" in the WinZip Self Extractor dialog to select the desired destination directory for the extracted file.
- Click on the "Unzip" button.
The ASCII data files will then be uncompressed into this directory. After the files are uncompressed, the *.exe files can be deleted.
KID documentation files on the HCUP-US Website (http://www.hcup-us.ahrq.gov) provide important resources for the user. Refer to these resources to understand the structure and content of the KID and to aid in using the database.
- To locate the KID documentation on HCUP-US, choose "Databases" from the home page (http://www.hcup-us.ahrq.gov). The section labeled KIDS’ Inpatient Database (KID) is specific to the KID.
HOW TO USE THE KID FOR DATA ANALYSIS
This section provides a brief synopsis of special considerations when using the KID. For more details, refer to the comprehensive documentation on the HCUP-US Website (http://www.hcup-us.ahrq.gov).
- If anyone other than the original purchaser uses the KID data, be sure to have them read and sign a Data Use Agreement, after viewing the on-line Data Use Agreement Training Tool available on the HCUP-US Website (http://www.hcup-us.ahrq.gov). A copy of the signed Data Use Agreements must be sent to AHRQ. See HCUP Contact Information for the mailing address.
- The KID contains discharge-level records, not patient-level records. This means that individual patients who are hospitalized multiple times in one year may be present in the KID multiple times. There is no uniform patient identifier available that allows a patient-level analysis with the KID. This will be especially important to remember for certain conditions for which patients may be hospitalized multiple times in a single year.
Calculating National Estimates
- To produce national estimates, use one of the following discharge weights to weight discharges in the KID Core files to pediatric discharges from all U.S. community, non-rehabilitation hospitals. The name of the discharge weight data element depends on the year of data and the type of analysis. In order to produce national estimates, you MUST use discharge weights.
|KID Data Year||Name of Discharge Weight on the Core File to Use for Creating Nationwide Estimates|
|2003 forward||• DISCWT for all analyses|
|2000||• DISCWT to create nationwide estimates for all analyses except those that involve total charges.
• DISCWTCHARGE to create nationwide estimates of total charges.
|1997||• DISCWT_U for all analyses|
- Similar to the NIS, proper statistical techniques must be used to calculate standard errors and confidence intervals when using the KID. For detailed instructions, refer to the special report Calculating Nationwide Inpatient Sample Variances on the HCUP-US Website (www.hcup-us.ahrq.gov). A report specific to the KID, Calculating Kids’ Inpatient Database (KID) Variances, is also available on www.hcup-us.ahrq.gov.
- The KID Comparison Reports (available on http://www.hcup-us.ahrq.gov) assess the accuracy of KID estimates. No comparison report was created for the 2000 KID. The updated report for the current KID will be posted on the HCUP-US Website (http://www.hcup-us.ahrq.gov) as soon as it is completed.
- When creating national estimates, it is a good idea to check your estimates against other data sources, if available. For example, the National Hospital Discharge Survey (http://www.cdc.gov/nchs/products/series.htm#sr13) can provide benchmarks against which to check your national estimates for hospitalizations with more than 5,000 discharges.
- To ensure that you are using the weights appropriately and calculating estimates and variances accurately, you can also use HCUPnet, the free online query system (https://hcupnet.ahrq.gov/#setup). HCUPnet is a Web-based query tool for identifying, tracking, analyzing, and comparing statistics on hospitals at the national, regional, and State level. HCUPnet offers easy access to national statistics and trends and selected State statistics about hospital stays. This tool provides step–by–step guidance, helping researchers to quickly obtain the statistics they need. HCUPnet generates statistics using the NIS, KID, and SID for those States that have agreed to participate. In addition, HCUPnet provides Quick Statistics — ready-to-use tables on commonly requested information — as well as national statistics based on the AHRQ Quality Indicators.
- When studying trends over time using the KID, be aware that the sampling frame for the KID changes over time (i.e., more States have been added). Estimates from earlier years of the KID may be subject to more sampling bias than later years of the KID. In order to facilitate analysis of trends using multiple years of KID data, an alternate set of KID discharge and hospital weights for the 1997 HCUP KID were developed. These alternative weights were calculated in the same way as the weights for the 2000 and later years of the KID. The report, Using the Kids’ Inpatient Database (KID) to Estimate Trends, includes details regarding the alternate weights and other recommendations for trends analysis. Both the KID trends report and the alternate weights are available on the HCUP-US Website under Methods Series (http://www.hcup-us.ahrq.gov/reports/methods/methods.jsp).
- Short-term rehabilitation hospitals are included in the 1997 KID, but are excluded from later years of the KID. Patients treated in short-term rehabilitation hospitals tend to have lower mortality rates and longer lengths of stay than patients in other community hospitals. The elimination of rehabilitation hospitals may affect trends but the effect is likely small since only about 3% of community hospitals are short-term rehabilitation hospitals and not all State data sources included short term rehabilitation hospitals. The KID-Trends weights account for this change in KID sampling.
Choosing Data Elements for Analysis
- For all data elements you plan to use in your analysis, first perform descriptive statistics and examine the range of values, including number of missing cases. Summary statistics for the entire KID are provided on the Summary Statistics page of the HCUP-US Website (http://hcup-us.ahrq.gov/db/nation/kid/kidsummarystats.jsp). When you detect anomalies (such as large numbers of missing cases), perform descriptive statistics by State for that variable to detect if there are State-specific differences. Sometimes performing descriptive statistics by hospital can be helpful in detecting hospital-specific data anomalies.
- Not all data elements in the KID are provided by each State data source. These data elements are provided on the KID because they can be valuable for research purposes but they should be used cautiously. For example, RACE is missing for a number of States; thus, national estimates using RACE should be interpreted and reported with caveats. Check the documentation and run frequencies by State to identify if a data element is not available in one or more States.
- Differences exist across the State data sources in the collection of information that could not be accounted for during HCUP processing to make the data uniform. Be sure to read State-specific notes for each data element that you use in your analysis – this information can be found on the Description of Data Elements page on the HCUP-US Website (http://hcup-us.ahrq.gov/db/nation/kid/kiddde.jsp).
- Data elements with "_X" suffixes contain State-specific coding (i.e., these data elements are provided by the data sources and have not been altered in any way). For some data elements (e.g., LOS_X and TOTCHG_X) this means that no edit checks have been applied. For other data elements (e.g., PAY1_X), the coding is specific to each State and may not be comparable to any other State.
ICD-9-CM Diagnosis and Procedure Codes
- ICD-9-CM diagnosis and procedure codes provide valuable insights into the reasons for hospitalization and what procedures patients receive, but these codes need to be carefully used and interpreted. ICD-9-CM codes change every October as new codes are introduced and some codes are retired. See the Conversion Table at http://www.cdc.gov/nchs/datawh/ftpserv/ftpicd9/ftpicd9.htm which shows ICD-9-CM code changes over time. It is critical to check all ICD-9-CM code used for analysis to ensure the codes are in effect during the time period studied.
- Although the KID contains up to 15 diagnoses and 15 procedures, the number of diagnoses and procedures varies by State. Some States provide as many as 30 diagnoses and 21 procedures, while other States provide as few as 9 diagnoses and 6 procedures. Because very few cases have more than 15 diagnoses or procedures, the diagnosis and procedure vectors were truncated to save space in the KID data files. Two variables are provided which tell you exactly how many diagnoses and procedures were on the original records (NDX and NPR).
- The collection and reporting of external cause of injury (E codes) varies greatly across States. Some States have laws or mandates for the collection of E codes; others do not. Some States do not require hospitals to report E codes in the range E870-E879 – "misadventures to patients during surgical and medical care" – which means that these occurrences will be underreported. Beginning with the 2003 KID, E codes have been separated from the other diagnoses stored in DX1-DX15 and placed in ECODE1-ECODE4. Be sure to read the State-specific notes on diagnoses for more details; this information can be found on the Description of Data Elements page on the HCUP-US Website (http://hcup-us.ahrq.gov/db/nation/kid/kiddde.jsp).
Missing data values can compromise the quality of estimates. If the outcome for discharges with missing values is different from the outcome for discharges with valid values, then sample estimates for that outcome will be biased and inaccurately represent the discharge population. There are several techniques available to help overcome this bias. One strategy is to use imputation to replace missing values with acceptable values. Another strategy is to use sample weight adjustments to compensate for missing values.1 Descriptions of such data preparation and adjustment are outside the scope of this report; however, it is recommended that researchers evaluate and adjust for missing data, if necessary.
On the other hand, if the cases with and without missing values are assumed to be similar with respect to their outcomes, no adjustment may be necessary for estimates of means and rates. This is because the non-missing cases would be representative of the missing cases. However, some adjustment may still be necessary for the estimates of totals. Sums of data elements (such as aggregate charges) containing missing values would be incomplete because cases with missing values would be omitted from the calculations.
It may be important for researchers to calculate a measure of precision for some estimates based on the KID sample data. Variance estimates must take into account both the sampling design and the form of the statistic. If hospitals inside the frame are similar to hospitals outside the frame, the sample hospitals can be treated as if they were randomly selected from the entire universe of hospitals within each stratum. Discharges were randomly selected from within each hospital. Standard formulas for stratified, two-stage cluster samples without replacement may be used to calculate statistics and their variances in most applications. To accurately calculate variances from the KID, you must use appropriate statistical software and techniques. For details, see the special report, Calculating Kids’ Inpatient Database (KID) Variances. This report is available on the HCUP-US Website at http://www.hcup-us.ahrq.gov/db/nation/kid/kidrelatedreports.jsp.
A multitude of statistics can be estimated from the KID data. Several computer programs that calculate statistics and their variances from sample survey data are listed in the section below. Some of these programs use general methods of variance calculations (e.g., the jackknife and balanced half-sample replications) that take into account the sampling design. However, it may be desirable to calculate variances using formulas specifically developed for some statistics.
These variance calculations are based on finite-sample theory, which is an appropriate method for obtaining cross-sectional, nationwide estimates of outcomes. According to finite-sample theory, the intent of the estimation process is to obtain estimates that are precise representations of the nationwide population at a specific point in time. In the context of the KID, any estimates that attempt to accurately describe characteristics (such as expenditure and utilization patterns or hospital market factors) and interrelationships among characteristics of hospitals and discharges during a specific year should be governed by finite-sample theory.
Alternatively, in the study of hypothetical population outcomes not limited to a specific point in time, the concept of a "superpopulation" may be useful. Analysts may be less interested in specific characteristics from the finite population (and time period) from which the sample was drawn than they are in hypothetical characteristics of a conceptual superpopulation from which any particular finite population in a given year might have been drawn. According to this superpopulation model, the nationwide population in a given year is only a snapshot in time of the possible interrelationships among hospital, market, and discharge characteristics. In a given year, all possible interactions between such characteristics may not have been observed, but analysts may wish to predict or simulate interrelationships that may occur in the future.
Under the finite-population model, the variances of estimates approach zero as the sampling fraction approaches one. This is the case because the population is defined at that point in time, and because the estimate is for a characteristic as it existed when sampled. This is in contrast to the superpopulation model, which adopts a stochastic viewpoint rather than a deterministic viewpoint. That is, the nationwide population in a particular year is viewed as a random sample of some underlying superpopulation over time. Different methods are used for calculating variances under the two sample theories. The choice of an appropriate method for calculating variances for nationwide estimates depends on the type of measure and the intent of the estimation process.
Computer Software for Variance Calculations
The discharge weights would be used to weight the sample data in estimating population statistics. In most cases, computer programs are readily available to perform these calculations. Several statistical programming packages allow weighted analyses.2 For example, nearly all SAS procedures incorporate weights. In addition, several statistical analysis programs have been developed to specifically calculate statistics and their standard errors from survey data. Version eight or later of SAS contains procedures (PROC SURVEYMEANS and PROC SURVEYREG) for calculating statistics based on specific sampling designs. STATA and SUDAAN are two other common statistical software packages that perform calculations for numerous statistics arising from the stratified, single-stage cluster sampling design. Examples of the use of SAS, SUDAAN, and STATA to calculate KID variances are presented in the special report: Calculating Kids’ Inpatient Database (KID) Variances. This report is available on the HCUP-US Website at http://www.hcup-us.ahrq.gov/db/nation/kid/kidrelatedreports.jsp. For an excellent review of programs to calculate statistics from survey data, visit the following Website: http://www.hcp.med.harvard.edu/statistics/survey-soft/.
The KID database includes a Hospital file with variables required to calculate finite population statistics. The file includes hospital identifiers (Primary Sampling Units or PSUs), stratification variables, and stratum-specific totals for the numbers of discharges and hospitals so that finite-population corrections can be applied to variance estimates.
In addition to these subroutines, standard errors can be estimated by validation and cross-validation techniques. Given that a very large number of observations will be available for most analyses, it may be feasible to set aside a part of the data for validation purposes. Standard errors and confidence intervals can then be calculated from the validation data.
If the analytical file is too small to set aside a large validation sample, cross-validation techniques may be used. For example, tenfold cross-validation would split the data into ten equal-sized subsets. The estimation would take place in ten iterations. In each iteration, the outcome of interest is predicted for one-tenth of the observations by an estimate based on a model fit to the other nine-tenths of the observations. Unbiased estimates of error variance are then obtained by comparing the actual values to the predicted values obtained in this manner.
Finally, it should be noted that a large array of hospital-level variables are available for the entire universe of hospitals, including those outside the sampling frame. For instance, the variables from the AHA surveys and from the Medicare Cost Reports are available for nearly all hospitals in the U.S, although hospital identifiers are suppressed in the KID for a number of States. For these States, it will not be possible to link to outside hospital-level data sources. To the extent that hospital-level outcomes correlate with these variables, they may be used to sharpen regional and nationwide estimates.
SAMPLING OF DISCHARGES
Sampling of Discharges Included in the KID
Unlike the HCUP Nationwide Inpatient Sample (NIS), the KID does not involve sampling hospitals. Instead, the KID includes a sample of pediatric discharges from all hospitals in the sampling frame. For the sampling, pediatric discharges in all participating States are stratified by uncomplicated in-hospital birth, complicated in-hospital birth, and all other pediatric cases. To further ensure an accurate representation of each hospital's pediatric case-mix, the discharges are sorted by State, hospital, DRG, and a random number within each DRG. Systematic random sampling is used to select 10% of uncomplicated in-hospital births and 80% of complicated in-hospital births and other pediatric cases from each frame hospital.
To obtain national estimates, discharge weights are developed using the AHA universe as the standard. For the weights, hospitals are post-stratified on six characteristics contained in the AHA hospital files. These were the same characteristics used to define the NIS sampling strata (ownership/control, bedsize, teaching status, rural/urban location, and U.S. region), with the addition of a stratum for freestanding children's hospitals. If there were fewer than two frame hospitals, 30 uncomplicated births, 30 complicated births, and 30 non-birth pediatric discharges sampled in a stratum, that stratum is combined with an "adjacent" stratum containing hospitals with similar characteristics. Discharge weights are created by stratum in proportion to the number of AHA newborns for newborn discharges and in proportion to the total number of (non-newborn) AHA discharges for non-newborn discharges.
The KID Hospital Universe
The hospital universe is defined as all hospitals located in the U.S. that were open during any part of the calendar year and that were designated as community hospitals in the AHA Annual Survey Database. The AHA defines community hospitals as follows: "All non-Federal, short-term, general, and other specialty hospitals, excluding hospital units of institutions." Starting in 2005, the AHA included long term acute care facilities in the definition of community hospitals. These facilities provide acute care services to patients who need long term hospitalization (more than 25 days stays). Consequently, Veterans Hospitals and other Federal facilities (Department of Defense and Indian Health Service) are excluded. Beginning with the 2000 KID, short-term rehabilitation hospitals were excluded from the universe, because the type of care provided and the characteristics of the discharges from these facilities were markedly different from other short-term hospitals. (The 1997 KID includes short-term rehabilitation hospitals.) Table 2 (Appendix I) displays the number of hospitals in the universe for each year, based on the corresponding AHA Annual Survey Database.
For more information on how hospitals in the data set were mapped to hospitals as defined by the AHA, refer to the special report, HCUP Hospital Identifiers. For a list of all data sources, refer to Table 1 in Appendix I. Detailed information on the design of the KID prior to 2006 is available in the year-specific special reports on Design of the Kids’ Inpatient Database found on the HCUP-US website. Starting with the 2006 KID, the design information was incorporated into this report.
Hospital Merges, Splits, and Closures
All U.S. hospital entities that were designated community hospitals in the AHA hospital file, except short-term rehabilitation hospitals, were included in the hospital universe. Therefore, when two or more community hospitals merged to create a new community hospital, the original hospitals and the newly-formed hospital were all considered separate hospital entities in the universe during the year they merged. Similarly, if a community hospital split, the original hospital and all newly-created community hospitals were treated as separate entities in the universe during the year this occurred. Finally, community hospitals that closed during a given year were included in the hospital universe, as long as they were in operation during some part of the calendar year.
For the purpose of calculating discharge weights, we post-stratified hospitals on six characteristics contained in the AHA hospital files. These were the same characteristics used to define the HCUP Nationwide Inpatient Sample (NIS) sampling strata, with the addition of a stratum for stand-alone children’s hospitals. The definitions of some of the NIS strata were revised for 1998 and subsequent data years, and we used the revised strata beginning with the 2000 KID. (A description of the strata used for the 1997 KID can be found in the Kids’ Inpatient Database (KID) Design Report, 1997. This report is available on the HCUP-US website at http://www.hcup-us.ahrq.gov/db/nation/kid/kidrelatedreports.jsp.)
Beginning with the 2000 KID, the stratification variables were defined as follows:
- Geographic Region – Northeast, Midwest, West, and South. This is an important stratification variable because practice patterns have been shown to vary substantially by region. For example, lengths of stay tend to be longer in East Coast hospitals than in West Coast hospitals. Figure 1 highlights the KID States by region, and Table 5 lists the States that comprise each region. Both can be found in Appendix I.
- Control – government non-Federal (public), private not-for-profit (voluntary), and private investor-owned (proprietary). These types of hospitals tend to have different missions and different responses to government regulations and policies. When there were enough hospitals of each type to allow it, hospitals were stratified as public, voluntary, and proprietary. This stratification was used for Southern rural, Southern urban non-teaching, and Western urban non-teaching hospitals. For smaller strata — the Midwestern rural and Western rural hospitals — a collapsed stratification of public versus private was used, with the voluntary and proprietary hospitals combined to form a single "private" category. For all other combinations of region, location, and teaching status, no stratification based on control was advisable, given the number of hospitals in these cells.
- Location – urban or rural. Government payment policies often differ according to this designation. Also, rural hospitals are generally smaller and offer fewer services than urban hospitals. Beginning with the 2006 KID, we changed the classification of urban or rural hospital location for the sampling strata to use the newer Core Based Statistical Area (CBSA) codes rather than the older Metropolitan Statistical Area (MSA) codes. The CBSA groups are based on 2000 Census data, whereas the MSA groups were based on 1990 Census data. Also, the criteria for classifying the counties differ. For more information on the difference between CBSAs and MSAs, refer to the U.S. Census Bureau website (http://www.census.gov/population/metro/.
Previously, we classified hospitals in an MSA as urban hospitals, while we classified hospitals outside a MSA as rural hospitals. Beginning with the 2006 KID, we categorized hospitals with a CBSA type of Metropolitan or Division as urban, while we designated hospitals with a CBSA type of Micropolitan or Rural as rural.
- Teaching Status – teaching or non-teaching. The missions of teaching hospitals differ from non-teaching hospitals. In addition, financial considerations differ between these two hospital groups. Currently, the Medicare DRG payments are uniformly higher to teaching hospitals. Prior to 2006, the teaching status of hospitals identified as children’s hospitals by the National Association of Children’s Hospitals and Related Institutions (NACHRI) was based on an indicator provided by NACHRI. The NACHRI teaching status indicator was not available for 2006. Therefore, for all hospitals, teaching status was determined using only information from the AHA Annual Survey Database.
In the 1997 KID, we considered other hospitals to be teaching hospitals if they had any residents or interns and met one of the following two criteria:
- Residency training approval by the Accreditation Council for Graduate Medical Education (ACGME)
- Membership in the Council of Teaching Hospitals (COTH).
Beginning with the 2000 KID, we considered other hospitals to be teaching hospitals if they met any one of the following three criteria:
- Residency training approval by the Accreditation Council for Graduate Medical Education (ACGME)
- Membership in the Council of Teaching Hospitals (COTH)
- A ratio of full–time equivalent interns and residents to beds of .25 or higher.3
- Bed Size – small, medium, and large. Bed size categories are based on hospital beds and are specific to the hospital's region, location, and teaching status, as illustrated in Table 6 of Appendix I. The bed size cutoff points were chosen so that approximately one–third of the hospitals in a given region, location, and teaching status combination would fall within each bed size category (small, medium, or large). Different cutoff points for rural, urban non-teaching, and urban teaching hospitals were used because hospitals in those categories tend to be small, medium, and large, respectively. For example, a medium–sized teaching hospital would be considered a rather large rural hospital. Further, the size distribution is different among regions for each of the urban/teaching categories. For example, teaching hospitals tend to be smaller in the West than they are in the South. Using differing cutoff points in this manner avoids strata containing small numbers of hospitals.
Rural hospitals were not split according to teaching status, because rural teaching hospitals were rare. For example, rural teaching hospitals generally comprise about 2% or less than the total hospital universe. The bed size categories were defined within location and teaching status because they would otherwise have been redundant. Rural hospitals tend to be small; urban non–teaching hospitals tend to be medium–sized; and urban teaching hospitals tend to be large. Yet it was important to recognize gradations of size within these types of hospitals. For example, in serving rural discharges, the role of "large" rural hospitals (particularly rural referral centers) often differs from the role of "small" rural hospitals.
- Hospital Type – freestanding children’s or other hospital Children’s hospitals restrict admissions to children, while other hospitals admit both adults and children. There may be significant differences in practice patterns, severity of illness, and available services between children’s hospitals and other hospitals. Data from NACHRI were used to help verify and correct the AHA list of children’s hospitals. Children’s units in general hospitals were not stratified as children’s hospitals.
Hospital Sampling Frame
The universe of hospitals was established as all community hospitals located in the U.S. with the exception, beginning in 2000, of short-term rehabilitation hospitals. However, some hospitals do not supply data to HCUP. Therefore, we constructed the KID sampling frame from the subset of universe hospitals that released their discharge data to AHRQ for research use. The number of State Partners and hospitals contributing data to the KID has expanded over the years, as shown in Table 2 of Appendix I.
The list of the entire frame of hospitals was composed of all AHA community, non-rehabilitation hospitals in each of the frame States that could be matched to the discharge data provided to HCUP. If an AHA hospital could not be matched to the discharge data provided by the data source, it was eliminated from the sampling frame (but not from the target universe).
Table 7 of Appendix I shows the number of AHA, HCUP SID, and KID hospitals by State. In most cases, the difference between the universe and the frame represents the difference between the number of community, non-rehabilitation hospitals in the 2006 AHA Annual Survey Database and the number of hospitals with children’s discharges that were supplied to HCUP that could be matched to the AHA data.
The largest discrepancy between HCUP data and AHA data is in Texas, as is evident in Table 7 of Appendix I. Certain Texas State-licensed hospitals are exempt from statutory reporting requirements. Exempt hospitals include:
- Hospitals that do not seek insurance payment or government reimbursement
- Rural providers.
The Texas statute that exempts rural providers from the requirement to submit data defines a hospital as a rural provider if it:
(I) Is located in a county that:
(A) Has a population estimated by the United States Bureau of the Census to be not more than 35,000 as of July 1 of the most recent year for which county population estimates have been published; or
(B) Has a population of more than 35,000, but does not have more than 100 licensed hospital beds and is not located in an area that is delineated as an urbanized area by the United States Bureau of the Census; and
These exemptions apply primarily to smaller rural public hospitals and, as a result, these facilities are less likely to be included in the sampling frame than other Texas hospitals. While the number of hospitals omitted appears sizable, those available for the KID include more than 90% of inpatient discharges from Texas universe hospitals because excluded hospitals tended to have relatively few discharges.
Beginning with the 2000 KID, pediatric discharges were defined as having an age at admission of 20 or less. This differs from the 1997 KID, which included discharges with an admission age of 18 or less. Discharges with missing, invalid, or inconsistent ages were excluded.
Hospital Sample Design
The overall design objective was to select a sample of pediatric discharges that accurately represents the target universe of U.S. community, non-rehabilitation hospitals. Moreover, this sample was to be geographically dispersed, yet drawn exclusively from hospitals in States that participate in HCUP and agree to contribute to the KID.
It should be possible, for example, to estimate DRG-specific average lengths of stay across all U.S. hospitals using weighted average lengths of stay, based on averages or regression coefficients calculated from the KID. Ideally, relationships among outcomes and their correlates estimated from the KID should accurately represent all U.S. hospitals. It is advisable to verify your estimates against other data sources, if available, because not all States contribute data to the KID. For example, the National Hospital Discharge Survey (http://www.cdc.gov/nchs/about/major/hdasd/nhds.htm) can provide benchmarks against which to check your national estimates for hospitalizations with more than 5,000 cases.
The KID Comparison Report assesses the accuracy of KID estimates by providing a comparison of the KID with other data sources. The most recent report is available on the HCUP-US website (http://www.hcup-us.ahrq.gov/db/nation/kid/kidrelatedreports.jsp).
In order to sample and project births up to the number of births reported by the AHA, which reports in-hospital births, the KID development team identified all in-hospital births in the KID data. We further separated the in-hospital births in HCUP data into uncomplicated births and complicated births. We sampled uncomplicated births at a lower rate because they have little variation in their outcomes.
To determine the best way to identify in-hospital births, we ran cross-tabulations of different combinations of variables on all cases that had any of the following possible birth indicators: age of zero days (AGEDAY=0), neonatal diagnosis (NEOMAT>=2), neonatal Major Diagnostic Category (MDC 15), or admission type of birth (ATYPE=4).4 Based on reviews of the cross-tabulations, the MDC 15 DRG definitions, and ICD-9-CM birth diagnosis codes, the following screen was devised for births: an in-hospital birth diagnosis code (any diagnosis code in the range V3000 - V3901 with a fourth digit of zero, indicating born in the hospital, and a fifth digit of zero or one, indicating delivered without mention of cesarean delivery, or delivered by cesarean delivery), without an admission source of another hospital or health facility (ASOURCE not equal to 2 or 3).
We classified neonates transferred from other facilities as pediatric non-births because they are not included in births reported by the AHA. An age of zero days was not a reliable in-hospital birth indicator because neonates transferred from another hospital or born before admission to the hospital could also have an age of zero days. There were also some cases with birth diagnoses, but with ages of a few days. Because the HCUP data are already edited for neonatal diagnoses inconsistent with age, we did not include any age criteria in the in-hospital birth screen.
Uncomplicated, in-hospital births are identified as cases that meet the above screen and are in DRG 391, "Normal Newborn." In the KID, a small percentage of the cases in DRG 391 do not meet the in-hospital birth screen. These cases have diagnoses that imply a newborn, but do not specifically indicate an in-hospital birth. It is possible that some of these may have actually been born in the hospital but lacked the proper diagnosis code. Others may be readmissions or may have been born before admission to the hospital. Some of these cases have an admission type of newborn (ATYPE = 4).
Changes to Sampling and Weighting Strategy Beginning with the 2000 KID
We use the NIS community hospital universe and strata definitions for the KID. We revised some of the NIS hospital universe and strata definitions for 1998 and subsequent data years, and we used these revised definitions beginning with the 2000 KID. These changes included:
- Revising definitions of the strata variables
- Excluding rehabilitation hospitals from the hospital universe
- Changing the calculation of hospital universe discharges for the weights.
A full description of the evaluation and revision of the NIS sampling strategy for 1998 and subsequent data years can be found in the special report, Changes in NIS Sampling and Weighting Strategy for 1998. This document is available on the HCUP-US website at http://www.hcup-us.ahrq.gov/db/nation/kid/kidrelatedreports.jsp.
The KID includes a sample of pediatric discharges from all hospitals in the sampling frame. For the sampling, we stratified the pediatric discharges by uncomplicated in-hospital birth, complicated in-hospital birth, and pediatric non-birth. To further ensure an accurate representation of each hospital’s pediatric case-mix, we also sorted the discharges by State, hospital, DRG, and a random number within each DRG. We then used systematic random sampling to select 10% of uncomplicated in-hospital births and 80% of other pediatric cases from each frame hospital.
It should be observed that the NIS includes 100% of the discharges from hospitals in the NIS sample. Consequently, in the NIS, outcomes can be estimated without sampling error for individual hospitals that are identified in the sample. However, the KID includes fewer than 100% of the pediatric discharges for each hospital in the database. Therefore, researchers will not be able to calculate hospital-specific outcomes with certainty.
To obtain national estimates, we developed discharge weights using the AHA universe as the standard. For the weights, we post-stratified hospitals on six characteristics contained in the AHA hospital files. These were the same characteristics used to define the NIS sampling strata, with the addition of a stratum for freestanding children’s hospitals. We also stratified the KID discharges according to whether the discharge was an uncomplicated in-hospital birth, a complicated in-hospital birth, or a non-newborn pediatric discharge. If there were fewer than two frame hospitals, 30 uncomplicated births, 30 complicated births, and 30 non-birth pediatric discharges sampled in a stratum, we merged that stratum with an "adjacent" stratum containing hospitals with similar characteristics.
The discharge weights were created by stratum, in proportion to the number of AHA discharges for newborns and non-newborns. Refer to the report Design of the HCUP Kids’ Inpatient Database (KID), 1997 for a discussion of the analysis and development of the KID weighting scheme. This report is available on the HCUP-US website at http://www.hcup-us.ahrq.gov/db/nation/kid/kidrelatedreports.jsp.
We used NACHRI data to help verify and correct the AHA list of children’s hospitals in the target universe. Many of these children’s hospitals are units of larger institutions (AHA hospital type 10). Consequently, we do not have separate reporting for them either in the AHA survey or in the HCUP SID. However, data analysts may find it useful to identify hospitals that contain children’s units, which can be accomplished using the NACHTYPE variable in the KID.
The discharge weights usually are constant for all discharges of the same type (uncomplicated in-hospital birth, complicated in-hospital birth, and other pediatric discharge) within a stratum. The only exceptions are for strata with sample hospitals that, according to the AHA files, were open for the entire year but contributed less than their full year of data to the KID. For those hospitals, we adjusted the number of observed discharges by a factor of 4 ÷ Q, where Q was the number of calendar quarters that the hospital contributed discharges to the KID. For example, when a sample hospital contributed only two quarters of discharge data to the KID, the adjusted number of discharges was double the observed number.
With that minor adjustment, each discharge weight is essentially equal to the number of AHA universe discharges that each sampled discharge represents in its stratum. This calculation was possible because the numbers of total discharges and births were available for every hospital in the universe from the AHA files.
Discharge weights to the universe were calculated by post-stratification. Hospitals were stratified on geographic region, urban/rural location, teaching status, bed size, control, and hospital type. In some instances, strata were collapsed for sample weight calculations. Within stratum k, for hospital i, each KID sample discharge's universe weight was calculated as:
Wik = [Tk / (Rk * Ak)] * (4 ÷ Qi)
In the birth strata (both complicated and uncomplicated):
- Tk is the total number of births reported in the AHA survey.
- Ak is the total number of adjusted births in the restricted sampling frame.
- In the uncomplicated birth strata, Rk is the frame sampling rate for uncomplicated in-hospital births calculated as the sum of the adjusted number of uncomplicated births sampled divided by the sum of the adjusted number of uncomplicated births in the restricted frame.
- In the complicated birth strata, Rk is the frame sampling rate for complicated in-hospital births.
In the non-newborn strata:
- Tk is the total number of non-newborns reported in the AHA survey.
- Ak is the total number of adjusted non-newborn discharges in the sampling frame.
- Rk is the frame sampling rate for non-newborns from all non-newborn discharges in the sampling frame.
Qi is the number of quarters of discharge data contributed by hospital i to the KID (usually Qi = 4).
Tk / Ak estimates the number of discharges in the population that is represented by each discharge in the sampling frame. Rk adjusts for the fact that we are taking a sample of the frame in each stratum.
Uncomplicated in-hospital births were sampled at a lower rate than other discharges because the variation in hospital outcomes for uncomplicated births is considerably less than that for other pediatric cases and because we expect research to focus much more on other pediatric patients. We sampled uncomplicated births at the nominal rate of 10% and sampled other pediatric discharges (complicated newborns and other pediatric cases) at the nominal rate of 80% from the discharges available in the (restricted) frame. To avoid rounding errors in the weights calculation, the actual sampling rate for a discharge type (uncomplicated in-hospital birth, complicated in-hospital birth, or non-birth pediatric discharge) in stratum k, Rk, was calculated as follows:
Rk = Sk / Hk
- Sk is the number of adjusted discharges sampled for the discharge type in stratum k.
- Hk is the number of adjusted discharges in the sampling frame for the discharge type in stratum k.
The AHA birth counts include both uncomplicated and complicated births. Therefore, the weights in the uncomplicated birth strata implicitly assume that the proportion of births that are uncomplicated in the frame is representative of the proportion of births that are uncomplicated in the population for each stratum. A similar assumption is made for complicated newborns.
Similarly, the non-birth AHA discharge counts include all non-birth discharges, not just non-birth pediatric discharges. Consequently, the weights in the non-birth strata implicitly assume that the proportion of non-birth discharges that are pediatric across the HCUP SID hospitals is the same as the proportion of non-birth discharges that are pediatric across the universe of AHA hospitals, in the aggregate within each hospital stratum.
Weight Data Elements
To produce nationwide estimates, use the discharge weights to extrapolate sampled discharges in the Core file to the discharges from all U.S. community, non-rehabilitation hospitals. Beginning with the 2003 KID, use DISCWT to calculate nationwide estimates for all analyses. For the 2000 KID, use DISCWT to create nationwide estimates for all analyses except those that involve total charges, and use DISCWTCHARGE to create nationwide estimates of total charges. For the 1997 KID, use DISCWT_U for all analyses.
THE FINAL KID SAMPLE
In Appendix I, we present tables and figures that summarize the final KID sample. Table 8 shows the number of hospitals and discharges for children’s hospitals and other hospitals. For each hospital type, the table shows the number of:
- AHA universe hospitals and total discharges, including births
- Non-rehabilitation community hospitals in the SID and associated pediatric discharges
- Hospitals and pediatric discharges included in the KID.
Table 9 displays the unweighted and weighted number of uncomplicated births, complicated births, and pediatric non-births by hospital type in the KID.
Table 2 summarize information across all years of the KID, including the KID States, data sources, sample hospitals, and sample discharges.
Figure 2 displays the KID hospitals by geographic region. For each region, the chart presents:
- The number of hospitals in the AHA universe
- The number of SID community hospitals with pediatric discharges
- The number of hospitals in the KID (and the percentage of AHA universe hospitals).
Although pediatric discharges from hospitals in each region are selected for the KID, the comprehensiveness of the sampling frame varies by region, as shown in Figure 2.
Because the KID sampling frame has a disproportionate representation of the more populous States and contains hospitals with more annual discharges, its comprehensiveness in terms of discharges is higher. Figure 3 summarizes the estimated U.S. population by geographic region on July 1, 2006. For each region, the figure reveals:
- The estimated U.S. population
- The estimated population of States in the KID
- The percentage of estimated U.S. population included in KID States.
And, Figure 4 presents the number of discharges in the KID for each State in the sampling frame for 2006.
Special consideration was needed to handle the Massachusetts data in the 2006 KID. Fourth quarter data from sampled hospitals in Massachusetts were unavailable for inclusion in the 2006 KID. To account for the missing quarter of data, we sampled one fourth of the Massachusetts KID discharges from the first three quarters and modified the records to represent the fourth quarter. To ensure a representative sample, we sorted the Massachusetts KID discharges by hospital, discharge quarter, Clinical Classifications Software (CCS) diagnosis group for the principal diagnosis, gender, age, and a random number before selecting every fourth record. The following describes the adjustments made to the selected Massachusetts KID records:
- We relabeled the discharge quarter (DQTR) to four and saved the original discharge quarter in a new data element (DQTR_X).
- We adjusted the admission month (AMONTH) by the number of months corresponding to the change in the discharge quarter.
- We adjusted the total charges (TOTCHG and TOTCHG_X) using quarter-specific adjustment factors calculated as the mean total charges in the fourth quarter for all Northeastern KID States (excluding Massachusetts) divided by the mean total charges in the first, second, or third quarter for all Northeastern KID States (excluding Massachusetts).
We then adjusted the discharge weights for the Massachusetts records to appropriately account for the shifting of quarter one through three discharges to quarter four.
Appendix I: Tables and Figures
|AR||Arkansas Department of Health & Human Services|
|AZ||Arizona Department of Health Services|
|CA||Office of Statewide Health Planning & Development|
|CO||Colorado Hospital Association|
|FL||Florida Agency for Health Care Administration|
|GA||Georgia Hospital Association|
|HI||Hawaii Health Information Corporation|
|IA||Iowa Hospital Association|
|IL||Illinois Department of Public Health|
|IN||Indiana Hospital Association|
|KS||Kansas Hospital Association|
|KY||Kentucky Cabinet for Health and Family Services|
|MA||Division of Health Care Finance and Policy|
|MD||Health Services Cost Review Commission|
|MI||Michigan Health & Hospital Association|
|MN||Minnesota Hospital Association|
|MO||Hospital Industry Data Institute|
|NC||North Carolina Department of Health and Human Services|
|NE||Nebraska Hospital Association|
|NH||New Hampshire Department of Health & Human Services|
|NJ||New Jersey Department of Health & Senior Services|
|NV||Nevada Department of Health and Human Services|
|NY||New York State Department of Health|
|OH||Ohio Hospital Association|
|OK||Oklahoma State Department of Health|
|OR||Oregon Association of Hospitals and Health Systems|
|RI||Rhode Island Department of Health|
|SC||South Carolina State Budget & Control Board|
|SD||South Dakota Association of Healthcare Organizations|
|TN||Tennessee Hospital Association|
|TX||Texas Department of State Health Services|
|UT||Utah Department of Health|
|VA||Virginia Health Information|
|VT||Vermont Association of Hospitals and Health Systems|
|WA||Washington State Department of Health|
|WI||Wisconsin Department of Health & Family Services|
|WV||West Virginia Health Care Authority|
|Number of States||38||36||27||22|
|Data Sources||AR AZ CA CO CT FL GA HI IA IL IN KS KY MA MD MI MN MO NC NE NH NJ NV NY OH OK OR RI SC SD TN TX UT VA VT WA WI WV (Added AR and OK. ME and PA are not included)||AZ CA CO CT FL GA HI IA IL IN KS KY MD MA MI MN MO NC NE NH NJ NV NY OH OR RI SC SD TN TX UT VA VT WA WI WV (Added IL, IN, MI, MN, NE, NH, NV, OH, RI, SD, VT. ME and PA are not included)||AZ CA CO CT FL GA HI IA KS KY MD MA ME MO NC NJ NY OR PA SC TN TX UT VA WA WI WV (Added KY, ME, NC, TX, VA, WV. IL is not included)||AZ CA CO CT FL GA HI IL IA KS MD MA MO NJ NY OR PA SC TN UT WA WI|
|Hospitals||Community, non-rehabilitation hospitals||Community, non-rehabilitation hospitals||Community, non-rehabilitation hospitals||Community hospitals, including rehabilitation hospitals|
|Number of KID Hospitals||3,739||3,438||2,784||2,521|
|Hospital identifiers||Available for 24 out of 38 States||Available for 23 out of 36 States||Available for 19 out of 27 States||None – only general descriptors of hospital types|
|Definition of pediatric discharges||Age at admission of 20 years or less||Age at admission of 20 years or less||Age at admission of 20 years or less||Age at admission of 18 years or less|
|Number of pediatric discharges (unweighted)||3,131,324||2,984,129||2,516,833||1,905,797|
|Number of pediatric discharges (weighted)||7,558,812||7,409,162||7,291,032||6,657,326|
Figure 1. KID States, by Region
|Data from||Media/format options||Structure of Releases|
• 22 States
|On CD–ROM in ASCII format||1 year of data on one CD, compressed files
Beginning in 2003, a companion file with four different sets of severity measures
Beginning in 2006, a companion file with diagnosis and procedure groups
• 27 States
• 36 States
• 38 States
Restrictions on the Use of the KID
Description of the KID Files
Availability of Data Elements
Description of Data Elements in the KID
Corrections to the KID
Programs to load the ASCII data files into statistical software:
HCUP Tools: Labels and Formats
KID Related Reports
Links to HCUP-US page with various KID related reports such as the following:
HCUP Supplemental Files
|1: Northeast||Connecticut, Maine, Massachusetts, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont.|
|2: Midwest||Illinois, Indiana, Iowa, Kansas, Michigan, Minnesota, Missouri, Nebraska, North Dakota, Ohio, South Dakota, Wisconsin.|
|3: South||Alabama, Arkansas, Delaware, District of Columbia, Florida, Georgia, Kentucky, Louisiana, Maryland, Mississippi, North Carolina, Oklahoma, South Carolina, Tennessee, Texas, Virginia, West Virginia.|
|4: West||Alaska, Arizona, California, Colorado, Hawaii, Idaho, Montana, Nevada, New Mexico, Oregon, Utah, Washington, Wyoming.|
|Location and Teaching Status||Hospital Bed Size|
|State||AHA Universe Hospitals||SID Community, Non-Rehabilitation Hospitals||SID Community, Non-Rehabilitation Hospitals with Pediatric Discharges||KID Sampling- Frame Hospitals||KID Sample Hospitals|
|Hospital Type||Hospitals||Discharges (Including Births)||Hospitals with Pediatric Discharges||Pediatric Discharges||Hospitals||Pediatric Discharges|
|Not a Children's Hospital||5,045||38,881,991||3,836||6,027,890||3,694||2,841,194|
|Hospital Type||Uncomplicated Births||Complicated Births||Pediatric Non-Births||Total Pediatric Discharges|
|Not a Children's Hospital||255,908||740,183||1,845,103||2,841,194|
|Not a Children's Hospital||3,002,918||1,093,112||2,919,177||7,015,207|
Figure 2. Number of Hospitals in the 2006 AHA Universe, SID, and KID, by Region
Figure 3. Percentage of U.S. Population in 2006 KID States, by Region Calculated Using the Estimated U.S. population on July 1, 2006.7
Figure 4. Number of Discharges in the 2006 KID, by State
Appendix II: State-Specific Restrictions
The table below enumerates the types of restrictions applied to the KIDS’ Inpatient Database. Restrictions include the following types:
- Confidentiality of hospitals
- Confidentiality of records
- Confidentiality of physicians
- Missing discharges.
For each restriction type the data sources are listed alphabetically by State. Only data sources that have restrictions are included. Data sources that do not have restrictions are not included.
|Confidentiality of Hospitals - Restricted Identification of Hospitals|
|The following data sources required that hospitals not be identified in the KID:
|Confidentiality of Hospitals - Limitation on Sampling|
Limitations on sampling were needed for the following data sources:
|Confidentiality of Hospitals - Restricted Release of Stratifiers|
|Stratifier data elements were restricted for the following data sources to further ensure hospital confidentiality in the KID:
|Confidentiality of Records - Restricted Release of Age in Years, Age in Months, or Age in Days|
|The following data sources restrict or limit the release of age:
|Confidentiality of Records – Other Restrictions|
|The following data sources restrict or limit the release of data elements for patient confidentiality:
|Confidentiality of Physicians|
|The following data sources restrict the release of physician identifiers:
|In these states the following data elements are set to missing for all records:
|The following data sources may be missing discharge records for specific populations of patients:
Appendix III: Data Elements
Table 1. Data Elements in the KID Inpatient Core File
Note: Not all data elements in the KID are uniformly coded or available across all States. Each KID release differs in that some data elements were dropped, some were added, and the values of some data elements were changed.
Data elements that are italicized are not included in the 2006 KID, but are only available in previous years’ files.
|Coding Notes||Unavailable in 2006 for:|
|Admission day of week or weekend||AWEEKEND||2000, 2003, 2006||Admission on weekend: (0) admission on Monday-Friday, (1) admission on Saturday-Sunday|
|ADAYWK||1997||Admission day of week: (1) Sunday, (2) Monday, (3) Tuesday, (4) Wednesday, etc.|
|Admission month||AMONTH||1997, 2000, 2003, 2006||Admission month coded from (1) January to (12) December||CT, FL|
|Admission source||ASOURCE||1997, 2000, 2003, 2006||Admission source, uniform coding: (1) ER, (2) another hospital, (3) another facility including long-term care, (4) court/law enforcement, (5) routine/birth/other|
|ASOURCE_X||2000, 2003, 2006||Admission source, as received from data source using State-specific coding|
|ASOURCEUB92||2003, 2006||Admission source (UB-92 standard coding). For newborn admissions (ATYPE = 4): (1) normal delivery, (2) premature delivery, (3) sick baby, (4) extramural birth; For non-newborn admissions (ATYPE NE 4): (1) physician referral, (2) clinic referral, (3) HMO referral, (4) transfer from a hospital, (5) transfer from skilled nursing facility, (6) transfer from a another healthcare facility, (7) emergency room, (8) court/law enforcement, (A) transfer from a critical access hospital||CA, MD, RI|
|Admission type||ATYPE||1997, 2000, 2003, 2006||Admission type, uniform coding: (1) emergency, (2) urgent, (3) elective, (4) newborn, (5) trauma center beginning in 2003 data, (6) other||CA|
|ELECTIVE||2003, 2006||Indicates elective admission: (1) elective, (0) non-elective admission|
|Age at admission||AGE||1997, 2000, 2003, 2006||Age in years coded 0-124 years|
|AGEDAY||1997, 2000, 2003, 2006||Age in days coded 0-365 only when the age in years is less than 1||CT, FL, MA, NH, SC, TX|
|AGEMONTH||1997, 2000, 2003, 2006||Age in months (when age < 11 years)||CT, FL, SC, TX, VA|
|Birth weight||BWT||2000, 2003, 2006||Birth weight in grams||CA, FL, IA, IL, KS, MI, MN, MO, NE, NH, NV, NY, OH, OK, OR, SC, SD, TN, TX, UT, WA, WI, WV|
|Clinical Classifications Software (CCS) category||DXCCS1 - DXCCS15||2000, 2003, 2006||CCS category for all diagnoses|
|DCCHPR1||1997||CCS category for principal diagnosis in 1997. CCS was formerly called the Clinical Classifications for Health Policy Research (CCHPR)|
|PRCCS1 - PRCCS15||2000, 2003, 2006||CCS category for all procedures|
|PCCHPR1||1997||CCS category for principal procedure in 1997. CCS was formerly called the Clinical Classifications for Health Policy Research (CCHPR)|
|Diagnosis information||DX1 - DX15||1997, 2000, 2003, 2006||Diagnoses, principal and secondary (ICD-9-CM). Beginning in 2003, the diagnosis array does not include any of external cause of injury codes. These codes have been stored in a separate array ECODEn.|
|DXV1 - DXV15||1997||Diagnosis validity flags|
|HOSPBRTH||1997, 2000, 2003, 2006||Birth diagnosis, in this hospital|
|NDX||1997, 2000, 2003, 2006||Number of diagnoses coded on the original record|
|UNCBRTH||1997, 2000, 2003, 2006||Normal, uncomplicated birth in hospital|
|Diagnosis Related Group (DRG)||DRG||1997, 2000, 2003, 2006||DRG in use on discharge date|
|DRGVER||2000, 2003, 2006||Grouper version in use on discharge date|
|DRG10||1997||DRG Version 10 (effective October 1992 - September 1993)|
|DRG18||2000, 2003||DRG Version 18 (effective October 2000 - September 2001)|
|DRG24||2006||DRG Version 24 (effective October 2006 - September 2007)|
|Discharge quarter||DQTR||1997, 2000, 2003, 2006||Coded: (1) Jan - Mar, (2) Apr - Jun, (3) Jul - Sep, (4) Oct - Dec|
|DQTR_X||2006||Discharge quarter, as received from data source|
|Discharge weights||DISCWT||2000, 2003, 2006||Weight to discharges in AHA universe for national estimates. In 2000, the discharge weight DISCWTcharge should be used for estimates of total charges.|
|DISCWT_U||1997||Weight to discharges in AHA universe for national estimates.|
|DISCWTcharge||2000||Weight to discharges in AHA universe for total charge estimates.|
|Discharge year||YEAR||1997, 2000, 2003, 2006||Calendar year|
|Disposition of patient (discharge status)||DIED||1997, 2000, 2003, 2006||Indicates in-hospital death: (0) did not die during hospitalization, (1) died during hospitalization|
|DISP||1997||Disposition of patient, uniform coding in 1997: (1) routine, (2) short-term hospital, (3) skilled nursing facility, (4) intermediate care facility, (5) another type of facility, (6) home healthcare, (7) against medical advice, (20) died|
|DISPUB92||2000, 2003, 2006||Disposition of patient (UB-92 standard coding)||CA, IN, MD|
|DISPUNIFORM||2000, 2003, 2006||Disposition of patient, uniform coding used beginning in 1998: (1) routine, (2) transfer to short term hospital, (5) other transfers, including skilled nursing facility, intermediate care, and another type of facility, (6) home healthcare, (7) against medical advice, (20) died in hospital, (99) discharged alive, destination unknown|
|External causes of injury and poisoning||ECODE1 - ECODE4||2003, 2006||External cause of injury and poisoning code, primary and secondary (ICD-9-CM). Beginning in 2003, external cause of injury codes are stored in a separate array ECODEn from the diagnosis codes in the array DXn. Prior to 2003, these codes are contained in the diagnosis array (DXn).|
|E_CCS1 - E_CCS4||2003, 2006||CCS category for the external cause of injury and poisoning codes|
|NECODE||2003-2006||Number of external cause of injury codes on the original record.|
|Gender of patient||FEMALE||2000, 2003, 2006||Indicates gender for KID beginning in 1998: (0) male, (1) female|
|SEX||1997||Indicates gender in 1997 KID: (1) male, (2) female|
|Hospital information||DSHOSPID||2000, 2003, 2006||Hospital number as received from the data source||CT, GA, HI, IN, KS, MI, MO, NE, OH, OK, SC, SD, TN, TX|
|HOSPID||2000, 2003, 2006||HCUP hospital number (links to Hospital file)|
|HOSPNUM||1997||HCUP hospital number in 1997 (links to Hospital file)|
|HOSPST||2000, 2003, 2006||State postal code for the hospital (e.g., AZ for Arizona)|
|HOSPSTCO||2000||Modified Federal Information Processing Standards (FIPS) State/county code for the hospital links to Area Resource File (available from the Bureau of Health Professions, Health Resources and Services Administration). Beginning in 2003, this data element is available only on the hospital file.|
|KID_STRATUM||2000, 2003, 2006||Hospital stratum used for weights.|
|Length of Stay||LOS||1997, 2000, 2003, 2006||Length of stay, edited|
|LOS_X||1997, 2000, 2003, 2006||Length of stay, as received from data source|
|Location of the patient||PL_UR_CAT4||2003||Urban–rural designation for patient’s county of residence: (1) large metropolitan, (2) small metropolitan, (3) micropolitan, (4) non-core|
|PL_NCHS2006||2006||Urban–rural designation for patient's county of residence: (1) "Central" counties of metro areas >= 1 million population, (2) "Fringe" counties of metro areas >= 1 million population, (3) Counties in metro areas of 250,000 - 999,999 population, (4) Counties in metro areas of 50,000 - 249,999 population, (5) micropolitan counties, (6) non-core counties|
|Major Diagnosis Category (MDC)||MDC||1997, 2000, 2003, 2006||MDC in use on discharge date|
|MDC10||1997||MDC Version 10 (effective October 1992 - September 1993)|
|MDC18||2000, 2003||MDC Version 18 (effective October 2000 - September 2001)|
|MDC24||2006||MDC Version 24 (effective October 2006 - September 2007)|
|Median household income for patient's ZIP Code||ZIPINC_QRTL||2003, 2006||Median household income quartiles for patient's ZIP Code. Because these estimates are updated annually, the value ranges for the ZIPINC_QRTL categories vary by year. Check the HCUP-US website for details.|
|ZIPINC||2000||Median household income category in files beginning in 1998: (1) $1-$24,999, (2) $25,000-$34,999, (3) $35,000-$44,999, (4) $45,000 and above|
|ZIPINC4||1997||Median household income category in 1997: (1) $1-$25,000, (2) $25,001-$30,000, (3) $30,001-$35,000, (4) $35,001 and above|
|Neonatal/ maternal flag||NEOMAT||1997, 2000, 2003, 2006||Assigned from diagnoses and procedure codes: (0) not maternal or neonatal, (1) maternal diagnosis or procedure, (2) neonatal diagnosis, (3) maternal and neonatal on same record.|
|Payer information||PAY1||1997, 2000, 2003, 2006||Expected primary payer, uniform: (1) Medicare, (2) Medicaid, (3) private including HMO, (4) self-pay, (5) no charge, (6) other|
|PAY1_N||1997||Expected primary payer, nonuniform: (1) Medicare, (2) Medicaid, (3) Blue Cross, Blue Cross PPO, (4) commercial, PPO, (5) HMO, PHP, etc., (6) self-pay, (7) no charge, (8) Title V, (9) Worker's Compensation, (10) CHAMPUS, CHAMPVA, (11) other government, (12) other|
|PAY1_X||2000, 2003, 2006||Expected primary payer, as received from the data source|
|PAY2||1997, 2000, 2003, 2006||Expected secondary payer, uniform: (1) Medicare, (2) Medicaid, (3) private including HMO, (4) self-pay, (5) no charge, (6) other||AZ, CA, CO, FL, HI, IA, NH, OH, OK, RI, SD, VA|
|PAY2_N||1997||Expected secondary payer, nonuniform: (1) Medicare, (2) Medicaid, (3) Blue Cross, Blue Cross PPO, (4) commercial, PPO, (5) HMO, PHP, etc., (6) self-pay, (7) no charge, (8) Title V, (9) Worker's Compensation, (10) CHAMPUS, CHAMPVA, (11) other government, (12) other|
|PAY2_X||2000, 2003, 2006||Expected secondary payer, as received from the data source||AZ, CA, CO, FL, HI, IA, NH, OH, OK, RI, SD, VA|
|Physician identifiers, synthetic||MDNUM1_R||2003, 2006||Re-identified attending physician number in files starting in 2003||CA, CT, GA, HI, IL, IN, MA, NC, OH, OK, UT, VT, WI, WV|
|MDID_S||1997, 2000||Synthetic attending physician number in 1997 and 2000 KID|
|MDNUM2_R||2003, 2006||Re-identified secondary physician number in files starting in 2003||CA, CT, GA, HI, IL, IN, MA, NC, OH, OK, UT, VT, WI, WV|
|SURGID_S||1997, 2000||Synthetic second physician number in 1997 and 2000 KID|
|Procedure information||PR1 - PR15||1997, 2000, 2003, 2006||Procedures, principal and secondary (ICD-9-CM)|
|PRV1 -PRV15||1997||Procedure validity flag|
|NPR||1997, 2000, 2003, 2006||Number of procedures coded on the original record|
|PRDAY1||1997, 2000, 2003, 2006||Number of days from admission to principal procedure||IL, OH, OK, UT, WA, WV|
|PRDAY2 - PRDAY15||2000, 2003, 2006||Number of days from admission to secondary procedures|
|Race of Patient||RACE||1997, 2000, 2003, 2006||Race, uniform coding: (1) white, (2) black, (3) Hispanic, (4) Asian or Pacific Islander, (5) Native American, (6) other||GA, IL, KY, MN, NV, OH, OR, WA, WV|
|Record identifier, synthetic||RECNUM||1997, 2003, 2006||HCUP unique record number|
|KEY||2000||Unique record number for 2000 KID file|
|Total Charges||TOTCHG||1997, 2000, 2003, 2006||Total charges, edited|
|TOTCHG_X||1997, 2000, 2003, 2006||Total charges, as received from data source|
|Type of Data Element||HCUP Variable Name||Years Available||Coding Notes||Unavailable in 2006 for:|
|Universe Counts||N_DISC_U||1997, 2000, 2003, 2006||Number of universe discharges in the KID_STRATUM|
|N_BRTH_U||1997, 2000, 2003, 2006||Number of universe births in KID_STRATUM|
|N_HOSP_U||1997, 2000, 2003, 2006||Number of universe hospitals in KID_STRATUM|
|Sample Counts||S_DISC_U||1997, 2000, 2003, 2006||Number of sampled discharges in the sampling stratum (KID_STRATUM or STRATUM)|
|S_BRTH_U||1997, 2000, 2003, 2006||Number of sample births in KID_STRATUM|
|S_CHLD_U||1997, 2000, 2003, 2006||Number of sample pediatric non-births in KID_STRATUM|
|S_CMPB_U||1997, 2000, 2003, 2006||Number of sample complicated births in KID_STRATUM|
|S_UNCB_U||1997, 2000, 2003, 2006||Number of sample uncomplicated births in KID_STRATUM|
|S_HOSP_U||1997, 2000, 2003, 2006||Number of sample hospitals in KID_STRATUM|
|SID (Frame) Counts||PEDS_DISC||2000, 2003, 2006||Number of discharges, 20 years old or younger, from this hospital in the SID||GA|
|PEDS_PCT||2000, 2003, 2006||Percentage of hospital discharges, 20 years old or younger, from this hospital in the SID||GA|
|TOTAL_DISC||2000, 2003, 2006||Total number of discharges from this hospital in the SID||GA|
|TOTDSCHG||1997||Total number of discharges from this hospital in the SID|
|Hospital Identifiers||HOSPID||2000, 2003, 2006||HCUP hospital identification number (links to inpatient Core files)|
|HOSPNUM||1997||HCUP hospital identification number (links to inpatient Core files)|
|AHAID||2000, 2003, 2006||AHA hospital identifier that matches AHA Annual Survey Database||CT, GA, HI, IN, KS, MI, MO, NE, OH, OK, SC, SD, TN, TX|
|IDNUMBER||2000, 2003, 2006||AHA hospital identifier without the leading 6||CT, GA, HI, IN, KS, MI, MO, NE, OH, OK, SC, SD, TN, TX|
|HOSPNAME||2000, 2003, 2006||Hospital name from AHA Annual Survey Database||AR, CT, GA, HI, IN, KS, MI, MO, NE, OH, OK, SC, SD, TN, TX|
|NACHTYPE||1997, 2000, 2003, 2006||National Association of Children’s Hospitals and Related Institutions (NACHRI) hospital type: (0) not identified as a children’s hospital by NACHRI, (1) children’s general hospital, (2) children’s specialty hospital, (3) children’s unit in a general hospital||GA, NE, OK|
|Hospital Location||HOSPADDR||2000, 2003, 2006||Hospital address from AHA Annual Survey Database||AR, CT, GA, HI, IN, KS, MI, MO, NE, OH, OK, SC, SD, TN, TX|
|HOSPCITY||2000, 2003, 2006||Hospital city from AHA Annual Survey Database||AR, CT, GA, HI, IN, KS, MI, MO, NE, OH, OK, SC, SD, TN, TX|
|HOSPST||2000, 2003, 2006||Hospital State postal code for hospital (e.g., AZ for Arizona)|
|HOSPSTCO||2003, 2006||Modified Federal Information Processing Standards (FIPS) State/county code for the hospital links to Area Resource File (available from the Bureau of Health Professions, Health Resources and Services Administration)||CT, GA, HI, IN, KS, MI, MO, NE, OH, OK, SC, SD, TN, TX|
|HOSPZIP||2000, 2003, 2006||Hospital ZIP Code from AHA Annual Survey Database||AR, CT, GA, HI, IN, KS, MI, MO, NE, OH, OK, SC, SD, TN, TX|
|HFIPSSTCO||2006||Unmodified Federal Information Processing Standards (FIPS) State/county code for the hospital. Links to the Area Resource File (available from the Bureau of Health Professions, Health Resources and Services Administration)||CT, GA, HI, IN, KS, MI, MO, NE, OH, OK, SC, SD, TN, TX|
|Hospital Characteristics||KID_STRATUM||2000, 2003, 2006||Hospital stratum used for weights|
|STRATUM||1997||Hospital stratum used for weights in 1997|
|HOSP_BEDSIZE||2000, 2003, 2006||Bed size of hospital: (1) small, (2) medium, (3) large|
|H_BEDSZ||1997||Bed size of hospital: (1) small, (2) medium, (3) large|
|HOSP_CONTROL||2000, 2003, 2006||Control/ownership of hospital: (0) government or private, collapsed category, (1) government, nonfederal, public, (2) private, non-profit, voluntary, (3) private, invest-own, (4) private, collapsed category|
|H_CONTRL||1997||Control/ownership of hospital: (1) government, nonfederal (2) private, non-profit (3) private, invest-own|
|HOSP_LOCATION||2000, 2003, 2006||Location: (0) rural, (1) urban|
|H_LOC||1997||Location: (0) rural, (1) urban|
|HOSP_LOCTEACH||2000, 2003, 2006||Location/teaching status of hospital: (1) rural, (2) urban non-teaching, (3) urban teaching|
|H_LOCTCH||1997||Location/teaching status of hospital: (1) rural, (2) urban non-teaching, (3) urban teaching|
|HOSP_REGION||2000, 2003, 2006||Region of hospital: (1) Northeast, (2) Midwest, (3) South, (4) West|
|H_REGION||1997||Region of hospital: (1) Northeast, (2) Midwest, (3) South, (4) West|
|HOSP_TEACH||2000, 2003, 2006||Teaching status of hospital: (0) non-teaching, (1) teaching|
|H_TCH||1997||Teaching status of hospital: (0) non-teaching, (1) teaching|
|Discharge Years||YEAR||1997, 2000, 2003, 2006||Calendar year|
|Note: Because the following variables are not needed for calculating national estimates, they are not included in the 2006 KID Hospital file.|
|Discharge Weights||CHLDWT||2000||Weight to pediatric non-births in universe for national estimates. In 2000, the discharge weight CHLDWTcharge should be used for estimates of total charges.|
|CHLDWT_U||1997||Weight to pediatric cases in universe for national estimates. In the 1997 data, one weight CHLDWT_U is used to create all estimates.|
|CHLDWTCHARGE||2000||Weight to pediatric non-births in universe for total charge estimates|
|CMPBWT||2000||Weight to complicated births in universe for national estimates. In 2000, the discharge weight CMPBWTcharge should be used for estimates of total charges.|
|CMPBWTCHARGE||2000||Weight to complicated births in universe for total charge estimates|
|UNCBWT||2000||Weight to uncomplicated births in universe for national estimates. In 2000, the discharge weight UNCBWTcharge should be used for estimates of total charges.|
|UNCBWTCHARGE||2000||Weight to uncomplicated births in universe for total charge estimates|
|Frame Counts||H_BRTH_F||1997, 2000||Number of frame HCUP births in KID_STRATUM|
|H_CHLD_F||1997, 2000||Number of frame HCUP pediatric non-births in KID_STRATUM|
|H_CMPB_F||1997, 2000||Number of frame HCUP complicated births in KID_STRATUM|
|H_UNCB_F||1997, 2000||Number of frame HCUP uncomplicated births in KID_STRATUM|
|H_DISC_F||1997, 2000||Number of frame HCUP discharges in KID_STRATUM|
|H_HOSP_F||1997, 2000||Number of frame HCUP hospitals in KID_STRATUM|
|Sample Counts||S_CHLD||1997, 2000||Pediatric non-births sampled|
|S_CMPB||1997, 2000||Complicated births sampled|
|S_UNCB||1997, 2000||Uncomplicated births sampled|
|Type of Data Element||HCUP Variable Name||Years Available||Coding Notes|
|AHRQ Comorbidity Software (AHRQ)||CM_AIDS||2003, 2006||AHRQ comorbidity measure: Acquired immune deficiency syndrome|
|CM_ALCOHOL||2003, 2006||AHRQ comorbidity measure: Alcohol abuse|
|CM_ANEMDEF||2003, 2006||AHRQ comorbidity measure: Deficiency anemias|
|CM_ARTH||2003, 2006||AHRQ comorbidity measure: Rheumatoid arthritis/collagen vascular diseases|
|CM_BLDLOSS||2003, 2006||AHRQ comorbidity measure: Chronic blood loss anemia|
|CM_CHF||2003, 2006||AHRQ comorbidity measure: Congestive heart failure|
|CM_CHRNLUNG||2003, 2006||AHRQ comorbidity measure: Chronic pulmonary disease|
|CM_COAG||2003, 2006||AHRQ comorbidity measure: Coagulopathy|
|CM_DEPRESS||2003, 2006||AHRQ comorbidity measure: Depression|
|CM_DM||2003, 2006||AHRQ comorbidity measure: Diabetes, uncomplicated|
|CM_DMCX||2003, 2006||AHRQ comorbidity measure: Diabetes with chronic complications|
|CM_DRUG||2003, 2006||AHRQ comorbidity measure: Drug abuse|
|CM_HTN_C||2003, 2006||AHRQ comorbidity measure: Hypertension, uncomplicated and complicated|
|CM_HYPOTHY||2003, 2006||AHRQ comorbidity measure: Hypothyroidism|
|CM_LIVER||2003, 2006||AHRQ comorbidity measure: Liver disease|
|CM_LYMPH||2003, 2006||AHRQ comorbidity measure: Lymphoma|
|CM_LYTES||2003, 2006||AHRQ comorbidity measure: Fluid and electrolyte disorders|
|CM_METS||2003, 2006||AHRQ comorbidity measure: Metastatic cancer|
|CM_NEURO||2003, 2006||AHRQ comorbidity measure: Other neurological disorders|
|CM_OBESE||2003, 2006||AHRQ comorbidity measure: Obesity|
|CM_PARA||2003, 2006||AHRQ comorbidity measure: Paralysis|
|CM_PERIVASC||2003, 2006||AHRQ comorbidity measure: Peripheral vascular disorders|
|CM_PSYCH||2003, 2006||AHRQ comorbidity measure: Psychoses|
|CM_PULMCIRC||2003, 2006||AHRQ comorbidity measure: Pulmonary circulation disorders|
|CM_RENLFAIL||2003, 2006||AHRQ comorbidity measure: Renal failure|
|CM_TUMOR||2003, 2006||AHRQ comorbidity measure: Solid tumor without metastasis|
|CM_ULCER||2003, 2006||AHRQ comorbidity measure: Peptic ulcer disease excluding bleeding|
|CM_VALVE||2003, 2006||AHRQ comorbidity measure: Valvular disease|
|CM_WGHTLOSS||2003, 2006||AHRQ comorbidity measure: Weight loss|
|All Patient Refined DRG (3M)||APRDRG||2003, 2006||All Patient Refined DRG|
|APRDRG_Risk_Mortality||2003, 2006||All Patient Refined DRG: Risk of Mortality Subclass|
|APRDRG_Severity||2003, 2006||All Patient Refined DRG: Severity of Illness Subclass|
|All-Payer Severity-adjusted DRG (HSS, Inc.)||APSDRG||2003, 2006||All-Payer Severity-adjusted DRG|
|APSDRG_Mortality_Weight||2003, 2006||All-Payer Severity-adjusted DRG: Mortality Weight|
|APSDRG_LOS_Weight||2003, 2006||All-Payer Severity-adjusted DRG: Length of Stay Weight|
|APSDRG_Charge_Weight||2003, 2006||All-Payer Severity-adjusted DRG: Charge Weight|
|Disease Staging (Medstat)||DS_DX_Category1||2003, 2006||Disease Staging: Principal Disease Category|
|DS_Stage1||2003, 2006||Disease Staging: Stage of Principal Disease Category|
|DS_LOS_Level||2003, 2006||Disease Staging: Length of Stay Level|
|DS_LOS_Scale||2003, 2006||Disease Staging: Length of Stay Scale|
|DS_Mrt_Level||2003, 2006||Disease Staging: Mortality Level|
|DS_Mrt_Scale||2003, 2006||Disease Staging: Mortality Scale|
|DS_RD_Level||2003, 2006||Disease Staging: Resource Demand Level|
|DS_RD_Scale||2003, 2006||Disease Staging: Resource Demand Scale|
|Linkage Variables||HOSPID||2003, 2006||HCUP hospital identification number|
|RECNUM||2003, 2006||HCUP record identifier|
|Type of Data Element||HCUP Variable Name||Years Available||Coding Notes|
|Clinical Classifications Software category for Mental Health and Substance Abuse (CCS-MHSA)||CCSMGN1 – CCSMGN15||2006||CCS-MHSA general category for all diagnoses|
|CCSMSP1 – CCSMSP15||2006||CCS-MHSA specific category for all diagnoses|
|ECCSMGN1 – ECCSMGN4||2006||CCS-MHSA general category for all external cause of injury codes|
|Chronic Condition Indicator||CHRON1 – CHRON15||2006||Chronic condition indicator for all diagnoses: (0) non-chronic condition, (1) chronic condition|
|CHRONB1 – CHRONB15||2006||Chronic condition indicator body system for all diagnoses: (1) Infectious and parasitic disease, (2) Neoplasms, (3) Endocrine, nutritional, and metabolic diseases and immunity disorders, (4) Diseases of blood and blood-forming organs, (5) Mental disorders, (6) Diseases of the nervous system and sense organs, (7) Diseases of the circulatory system, (8) Diseases of the respiratory system, (9) Diseases of the digestive system, (10) Diseases of the genitourinary system, (11) Complications of pregnancy, childbirth, and the puerperium, (12) Diseases of the skin and subcutaneous tissue, (13) Diseases of the musculoskeletal system, (14) Congenital anomalies, (15) Certain conditions originating in the perinatal period, (16) Symptoms, signs, and ill-defined conditions, (17) Injury and poisoning, (18) Factors influencing health status and contact with health services|
|Procedure Class||PCLASS1 – PCLASS15||2006||Procedure Class for all procedures: (1) Minor Diagnostic, (2) Minor Therapeutic, (3) Major Diagnostic, (4) Major Therapeutic|
|Linkage Variables||HOSPID||2006||HCUP hospital identification number|
|RECNUM||2006||HCUP record identifier|
1 Refer to Chapter 10 in Foreman, E.K., Survey Sampling Principles. New York: Dekker, 1991.
2 Carlson BL, Johnson AE, Cohen SB. "An Evaluation of the Use of Personal Computers for Variance Estimation with Complex Survey Data." Journal of Official Statistics, vol. 9, no. 4, 1993: 795-814.
3 We used the following American Hospital Association Annual Survey Database (Health Forum, LLC © 2012) data elements to assign the KID Teaching Hospital Indicator:
AHA Data Element Name = Description [HCUP Data Element Name].
BDH = Number of short term hospital beds [B001H].
BDTOT = Number of total facility beds [B001].
FTRES = Number of full time employees: interns & residents (medical & dental) [E125].
PTRES = Number of part-time employees: interns & residents (medical & dental) [E225].
MAPP8 = Council of Teaching Hospitals (COTH) indicator [A101].
MAPP3 = Residency training approval by the Accreditation Council for Graduate Medical Education (ACGME) [A102].
Prior to the 1998 KID, we used the following SAS code to assign the KID teaching hospital status indicator, H_TCH:
/* FIRST ESTABLISH SHORT-TERM BEDS DEFINITION */
IF BDH NE . THEN BEDTEMP = BDH ; /* SHORT TERM BEDS */
ELSE IF BDH =. THEN BEDTEMP=BDTOT ; /* TOTAL BEDS PROXY */
/* NEXT ESTABLISH TEACHING STATUS BASED ON F-T & P-T */
/* RESIDENT/INTERN STATUS FOR HOSPITALS.
RESINT = (FTRES + .5*PTRES)/BEDTEMP ;
IF RESINT > 0 & (MAPP3=1 or MAPP8=1) THEN H_TCH=1;/* 1=TEACHING */
ELSE H_TCH=0 ; /* 0=NONTEACHING */
Beginning with the 1997 KID, we used the following SAS code to assign the teaching hospital status indicator, HOSP_TEACH:
/* FIRST ESTABLISH SHORT-TERM BEDS DEFINITION */
IF BDH NE . THEN BEDTEMP = BDH ; /* SHORT TERM BEDS */
ELSE IF BDH =. THEN BEDTEMP = BDTOT ; /* TOTAL BEDS PROXY */
/* ESTABLISH IRB NEEDED FOR TEACHING STATUS */
/* BASED ON F-T P-T RESIDENT INTERN STATUS */
IRB = (FTRES + .5*PTRES) / BEDTEMP ;
/* CREATE TEACHING STATUS VARIABLE */
IF (MAPP8 EQ 1) OR (MAPP3 EQ 1) THEN HOSP_TEACH = 1 ;
ELSE IF (IRB GE 0.25) THEN HOSP_TEACH = 1 ;
ELSE HOSP_TEACH = 0;
4 We performed this analysis during the development of the original 1997 KID.
5 Most AHA surveys do not cover a January-to-December calendar year for every hospital. The numbers of hospitals for the KID are based on the AHA Annual Survey files.
6 The columns in Table 7 are defined as follows:
- "AHA Universe Hospitals" lists all community, non-rehabilitation hospitals in the AHA Survey data.
- "SID Community, Non-Rehabilitation Hospitals" lists potential KID sampling-frame hospitals before applying restrictions to the frame and before excluding hospitals without any pediatric discharges.
- "SID Community, Non-Rehabilitation Hospitals with Pediatric Discharges" lists potential KID sampling-frame hospitals with pediatric discharges before applying restrictions to the frame.
- "KID Sampling-Frame Hospitals" lists hospitals with pediatric discharges in the sampling frame after applying state-specific restrictions to the frame.
- "KID Sample Hospitals" lists the hospitals selected for the KID. Some hospitals may not be included in the KID because they had so few pediatric discharges that none were randomly sampled.
7 Table 1: Annual Estimates of the Population for the United States, Regions, States, and Puerto Rico: April 1, 2000 to July 1, 2007 (NST-EST2007-01). Source: Population Division, U.S. Census Bureau. Release Date: December 27, 2007.
1 Community hospitals, as defined by the American Hospital Association (AHA), include "all non-Federal, short term, general, and other specialty hospitals, excluding hospital units of institutions." Included among community hospitals are specialty hospitals such as obstetrics gynecology, ear nose throat, short-term rehabilitation, orthopedic, and pediatric institutions. Also included are public hospitals and academic medical centers. Starting in 2005, the AHA included long term acute care facilities in the definition of community hospitals. These facilities provide acute care services to patients who need long term hospitalization (stays of more than 25 days). Excluded from the KID are short-term rehabilitation hospitals (beginning with 2000 data), long-term non-acute care hospitals, psychiatric hospitals, and alcoholism/chemical dependency treatment facilities.
|Internet Citation: 2006 Introduction to the KID. Healthcare Cost and Utilization Project (HCUP). June 2016. Agency for Healthcare Research and Quality, Rockville, MD. www.hcup-us.ahrq.gov/db/nation/kid/kid_2006_introduction.jsp.|
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