Detection of Inpatient Health Care Associated Injuries: Comparing Two ICD-9-CM Code Classifications

Abstract

This paper compares two complementary International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) code classifications for detection of adverse events (AEs) at the hospital, State, and national levels. The classifications are the Agency for Healthcare Research and Quality's Patient Safety Indicators 2003, June release, Version 2.1 (PS Indicators) and the Utah/Missouri Adverse Event Classification 2002, Version 1 (AE Classes). First, the paper describes similarities and differences between the two classifications, such as intended purpose, process of development, grouping of ICD-9-CM codes, specificity, and sensitivity. Second, it compares the ways each classification categorizes ICD-9-CM codes into indicators or classes of potential AEs. Third, the paper presents the number and percentage of Utah inpatient discharges (UTIDs) with any PS Indicator over 3 years (2000, 2001, and 2002) and compares the percentage of UTIDs by PS Indicator to published values derived from a national database, the Healthcare Cost and Utilization Project (HCUP) Nationwide Inpatient Sample 2000 (NIS). UTIDs have significantly higher values for five PS Indicators and significantly lower values for seven PS Indicators than NIS. Fourth, the paper presents the annual percentage of UTIDs with any AE Class code for 2000, 2001, and 2002, which shows a small but significant increase over this 3-year period. The AE Classes are more sensitive; they detect far more potential injuries due to medical care, or AEs, but may include more false positives than the PS Indicators. The PS Indicators are more specific; they detect fewer potential AEs but may include fewer false positives than the AE Classes.