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NRD Description of Data Elements

The following links provide data elements descriptions for the Nationwide Readmissions Database (NRD).

Data element descriptions explain how the data element is coded in the HCUP databases, and what are the uniform values. The descriptions are cumulative across all years of the NRD. Please note the following:
  • Not all data elements in the NRD are uniformly coded across States.
  • Not all data elements are available each year.
For certain data elements such as, but not limited to, total charges (TOTCHG), more than one percent of NRD records have missing values. Users are advised to review frequencies for all data elements planned for use in their analysis and to consider analytic methods for dealing with missing data. The HCUP Methods Series Report #2015-01 (PDF file, 871 KB) provides guidance on alternative approaches to handling missing data.

As a result of the introduction of ICD-10-CM/PCS1 on October 1, 2015 (quarter 4 of 2015 and the start of fiscal year 2016), the United States transitioned from using ICD-9-CM to ICD-10-CM/PCS code sets for reporting clinical diagnoses and inpatient procedures. Beginning with the quarter 4 of 2015, the names of diagnosis- and procedure-related data elements in the NRD start with the prefix "I10_" to identify the coding scheme. The coding change in 2015 also is signaled by a change in the NRD file structure:
  • The 2015 NRD included nine months of data with ICD-9-CM coding and three months of data with ICD-10-CM/PCS coding because of the mid-year change in diagnosis and procedure coding. The 2015 NRD files had a very different structure than other years and were split into two parts based on the diagnosis and procedure coding system.
  • Beginning with data year 2016, the NRD is an annual, calendar year file with diagnosis and procedure codes reported using only the ICD-10-CM/PCS coding system. Therefore, the file structure is similar to the file structure of the NRD in data years prior to 2015.
Data elements derived from AHRQ software tools which are based on ICD-10-CM/PCS diagnosis and/or procedure codes are not available on the NRD starting in quarter 4 of 2015. For users interested in applying the AHRQ software tools to the ICD-10-CM/PCS-coded data, the AHRQ software tools are available for download on the HCUP Tools & Software section of the HCUP User Support (HCUP-US) website. The Tools Loading tutorial is available to users interested in applying the AHRQ software tools at www.hcup-us.ahrq.gov/tech_assist/tutorials.jsp.

1 ICD-9-CM: International Classification of Diseases, Ninth Revision, Clinical Modification; ICD-10-CM/PCS: International Classification of Diseases, Tenth Revision, Clinical Modification/Procedure Coding System


All NRD data elements are listed in alphabetical order below, showing the NRD file location for years other than 2015 and for 2015. For a description of how HCUP data elements are coded, and uniform values, check the corresponding boxes below and then click the "View Description of Data Elements".
Check the corresponding boxes and then click

Abbreviations: DX, diagnosis; PR, procedure; Q1, discharge quarter 1; Q3, discharge quarter 3; Q4, discharge quarter 4.

HCUP Data Element Descriptive Title Years File(s) for years other than 2015 File(s) in 2015
Data elements change frequently, and are only current as of the date generated.
Age in years at admission 2010-2017 Core Core
All Patient Refined DRG 2010-2017 Severity Q1Q3 and Q4 Severity
All Patient Refined DRG: Risk of Mortality Subclass 2010-2017 Severity Q1Q3 and Q4 Severity
All Patient Refined DRG: Severity of Illness Subclass 2010-2017 Severity Q1Q3 and Q4 Severity
Admission day is on a weekend 2010-2017 Core Core
ICD-9-CM Body system n 2014-2015 Q3 DX_PR_Grps Q1Q3 DX_PR_Grps (not in Q4)
Chronic Condition Indicators - body system 2010-2013 DX_PR_Grps  
ICD-9-CM Chronic Condition Indicators 2010-2015 Q3 DX_PR_Grps Q1Q3 DX_PR_Grps (not in Q4)
AHRQ comorbidity measure for ICD-9-CM codes: acquired immune deficiency syndrome 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
AHRQ comorbidity measure for ICD-9-CM codes: alcohol abuse 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
AHRQ comorbidity measure for ICD-9-CM codes: deficiency anemias 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
AHRQ comorbidity measure for ICD-9-CM codes: rheumatoid arthritis/collagen vascular diseases 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
AHRQ comorbidity measure for ICD-9-CM codes: chronic blood loss anemia 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
AHRQ comorbidity measure for ICD-9-CM codes: congestive heart failure 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
AHRQ comorbidity measure for ICD-9-CM codes: chronic pulmonary disease 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
AHRQ comorbidity measure for ICD-9-CM codes: coagulopathy 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
AHRQ comorbidity measure for ICD-9-CM codes: depression 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
AHRQ comorbidity measure for ICD-9-CM codes: diabetes, uncomplicated 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
AHRQ comorbidity measure for ICD-9-CM codes: diabetes with chronic complications 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
AHRQ comorbidity measure for ICD-9-CM codes: drug abuse 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
AHRQ comorbidity measure for ICD-9-CM codes: hypertension (combine uncomplicated and complicated) 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
AHRQ comorbidity measure for ICD-9-CM codes: hypothyroidism 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
AHRQ comorbidity measure for ICD-9-CM codes: liver disease 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
AHRQ comorbidity measure for ICD-9-CM codes: lymphoma 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
AHRQ comorbidity measure for ICD-9-CM codes: fluid and electrolyte disorders 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
AHRQ comorbidity measure for ICD-9-CM codes: metastatic cancer 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
AHRQ comorbidity measure for ICD-9-CM codes: other neurological disorders 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
AHRQ comorbidity measure for ICD-9-CM codes: obesity 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
AHRQ comorbidity measure for ICD-9-CM codes: paralysis 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
AHRQ comorbidity measure for ICD-9-CM codes: peripheral vascular disorders 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
AHRQ comorbidity measure for ICD-9-CM codes: psychoses 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
AHRQ comorbidity measure for ICD-9-CM codes: pulmonary circulation disorders 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
AHRQ comorbidity measure for ICD-9-CM codes: renal failure 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
AHRQ comorbidity measure for ICD-9-CM codes: solid tumor without metastasis 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
AHRQ comorbidity measure for ICD-9-CM codes: peptic ulcer disease excluding bleeding 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
AHRQ comorbidity measure for ICD-9-CM codes: valvular disease 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
AHRQ comorbidity measure for ICD-9-CM codes: weight loss 2010-2015 Q3 Severity Q1Q3 Severity (not in Q4)
Died during hospitalization 2010-2017 Core Core
Weight to discharges in the universe 2010-2017 Core Core
Disposition of patient, uniform coding 2010-2017 Core Core
Discharge month 2010-2017 Core Core
Discharge quarter 2010-2017 Core Core
DRG in use on discharge date 2010-2017 Core Q1Q3 and Q4 DX_PR_Grps
DRG in use on discharge date, calculated without POA 2010-2017 Core Q1Q3 and Q4 DX_PR_Grps
DRG or MS-DRG grouper version used on discharge date 2010-2017 Core Q1Q3 and Q4 DX_PR_Grps
Clinical Classifications Software (CCS): ICD-9-CM diagnosis classification 2010-2015 Q3 Core Q1Q3 DX_PR_Grps (not in Q4)
Multi-Level CCS for ICD-9-CM Diagnoses 2010-2015 Q3 DX_PR_Grps Q1Q3 DX_PR_Grps (not in Q4)
ICD-9-CM Diagnosis 2010-2015 Q3 Core Q1Q3 DX_PR_Grps (not in Q4)
Diagnosis codes ICD version indicator 2015-2017 Core Q1Q3 and Q4 DX_PR_Grps
Clinical Classifications Software (CCS) for ICD-9-CM External Cause of Injury Code 2010-2015 Q3 Core Q1Q3 DX_PR_Grps (not in Q4)
ICD-9-CM External Cause of Injury Code 2010-2015 Q3 Core Q1Q3 DX_PR_Grps (not in Q4)
Multi-Level CCS for ICD-9-CM External Cause of Injury Code 2010-2015 Q3 DX_PR_Grps Q1Q3 DX_PR_Grps (not in Q4)
Elective versus non-elective admission 2010-2017 Core Core
Indicator of sex 2010-2017 Core Core
Control/ownership of hospital 2010-2017 Hospital Hospital
HCUP indicator of emergency department record 2010-2017 Core Core
Bedsize of hospital 2010-2017 Hospital Hospital
HCUP NRD hospital identification number 2010-2017 Core, Hospital, Severity, Dx_Pr_Grps (Dx_Pr_Grps not available in 2016) Core, Hospital, Q1Q3 and Q4 Severity, Q1Q3 and Q4 Dx_Pr_Grps
Teaching status of hospital 2010-2017 Hospital Hospital
Hospital urban-rural designation 2010-2017 Hospital Hospital
ICD-10-CM Diagnosis 2015 Q4 - 2017 Core Q4 DX_PR_Grps
ICD-10-CM External Cause of Morbidity Code 2015 Q4 - 2016 Core Q4 DX_PR_Grps
Number of ICD-10-CM diagnoses on this discharge 2015 Q4 - 2017 Core Q4 DX_PR_Grps
Number of ICD-10-CM External Cause of Morbidity codes on this record 2015 Q4 - 2016 Core Q4 DX_PR_Grps
Number of ICD-10-PCS procedures on this discharge 2015 Q4 - 2017 Core Q4 DX_PR_Grps
ICD-10-PCS Procedure 2015 Q4 - 2017 Core Q4 DX_PR_Grps
HCUP NRD record identifier 2010-2017 Core, Severity, Dx_Pr_Grps (Dx_Pr_Grps not available in 2016) Core, Q1Q3 and Q4 Severity, Q1Q3 and Q4 Dx_Pr_Grps
Length of stay, cleaned 2010-2017 Core Core
MDC in effect on discharge date 2010-2017 Core Q1Q3 and Q4 DX_PR_Grps
MDC in use on discharge date, calculated without POA 2010-2017 Core Q1Q3 and Q4 DX_PR_Grps
Number of discharges in the universe for the stratum 2010-2017 Hospital Hospital
Number of hospitals in the universe for the stratum 2010-2017 Hospital Hospital
ICD-9-CM Number of chronic conditions 2010-2015 Q3 Core Q1Q3 DX_PR_Grps (not in Q4)
Number of ICD-9-CM diagnoses on this discharge 2010-2015 Q3 Core Q1Q3 DX_PR_Grps (not in Q4)
Number of ICD-9-CM External of Cause of Injury Codes on this Record 2010-2015 Q3 Core Q1Q3 DX_PR_Grps (not in Q4)
Number of ICD-9-CM procedures on this discharge 2010-2015 Q3 Core Q1Q3 DX_PR_Grps (not in Q4)
Days from "start date" to admission 2010-2017 Core Core
Stratum used to post-stratify hospital 2010-2017 Core, Hospital Core, Hospital
Patient linkage variable in the NRD 2010-2017 Core Core
Major operating room ICD-9-CM procedure indicator 2010-2015 Q3 Core Q1Q3 DX_PR_Grps (not in Q4)
Expected primary payer, uniform 2010-2017 Core Core
ICD-9-CM Procedure class 2010-2015 Q3 DX_PR_Grps Q1Q3 DX_PR_Grps (not in Q4)
Patient Location: NCHS Urban-Rural Code 2010-2017 Core Core
Clinical Classifications Software (CCS) for ICD-9-CM Procedures 2010-2015 Q3 Core Q1Q3 DX_PR_Grps (not in Q4)
Number of days from admission to procedure n 2014-2017 Core Q1Q3 and Q4 DX_PR_Grps
Multi-Level CCS for ICD-9-CM Procedures 2010-2015 Q3 DX_PR_Grps Q1Q3 DX_PR_Grps (not in Q4)
ICD-9-CM Procedure 2010-2015 Q3 Core Q1Q3 DX_PR_Grps (not in Q4)
Procedure codes ICD version indicator 2015-2017 Core Q1Q3 and Q4 DX_PR_Grps
A combined record involving transfer to rehabilitation, evaluation, or other aftercare 2010-2017 Core Core
Identifies patient as a resident of the State in which he or she received hospital care 2010-2017 Core Core
Number of discharges in the sample for the stratum 2010-2017 Hospital Hospital
Number of hospitals in the sample for the stratum 2010-2017 Hospital Hospital
Identifies transfer and same-day stay collapsed records 2010-2017 Core Core
Service line based on ICD-9 codes 2014-2015 Q3 Core Q1Q3 DX_PR_Grps (not in Q4)
Number of hospital discharges in the sample 2010-2017 Hospital Hospital
Total charges, cleaned 2010-2017 Core Core
Calendar year 2010-2017 Core, Hospital Core, Hospital
Median household income for patient's ZIP Code (based on current year) 2010-2017 Core Core

Abbreviations: DX, diagnosis; PR, procedure; Q1, discharge quarter 1; Q3, discharge quarter 3; Q4, discharge quarter 4.


Internet Citation: NRD Description of Data Elements. Healthcare Cost and Utilization Project (HCUP). December 2019. Agency for Healthcare Research and Quality, Rockville, MD. www.hcup-us.ahrq.gov/db/nation/nrd/nrddde.jsp.
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Last modified 12/12/19