The Colorado Health & Hospital Association Discharge Data Program provides ambulatory surgery data to HCUP in a single source file. The file contains discharge records from ambulatory surgery centers that are associated with acute care hospitals. Discharges from freestanding ambulatory surgery centers are not included.

1988 Record Counts. Ambulatory surgery data collection by Colorado officially commenced April 1988, for hospitals with more than 50 beds. Those under 50 beds were added January 1989. Colorado indicated that the total observations in 1988 are inflated because the data submitted by hospitals included observations from many outpatient settings, rather than being limited to only discharges from hospital-associated ambulatory surgery centers. This was corrected by 1989.

Beginning in 1991, Colorado supplied ambulatory surgery records separate from inpatient records. Colorado defined an ambulatory surgery record as a having less than an overnight stay with a principal ICD-9-CM procedure of 01.01 to 86.99 regardless of location. From 1988 to 1990, Colorado supplied abstracts for ambulatory surgeries in the same source files as the inpatient discharge abstracts, distinguished by a record type indicator. Starting in 1991, Colorado supplied inpatient and ambulatory surgery records in separate files. Only the ambulatory surgery discharges were retained in the HCUP SASD. The table below explains how the ambulatory surgery discharges were identified.

How Ambulatory Surgery Records Were Identified in Colorado Data

Using the standard HCUP criteria for assigning records to the 2003 SASD, the Colorado outpatient records are separated as follows:

• 99.3 % of records are included in the SASD
• 0.7 % of records are excluded.

Identifying Freestanding Facilities. Starting in 1998, the data element FREESTANDING identifies hospital-based and freestanding ambulatory surgery facilities. Prior to 1998, there are two identifiers on the SASD that allow a researcher to identify hospital based and freestanding ambulatory surgery centers.

• DSHOSPID is the facility identifier provided by the data source.
• AHAID is the facility identifier used by the American Hospital Association.

1997 Colorado SASD. There are 69 unique DSHOSPID values in the 1997 CO SASD. All should be considered hospital-based facilities.