Risk adjustment using administrative data - Impact of a diagnosis-type indicator

OBJECTIVES: To determine the frequency with which commonly coded clinical v ariables are complications, as opposed to baseline comorbidities, and to co mpare the results of 2 risk-adjusted outcome analyses for coronary artery b ypass graft surgery for which we either (a) ignored, or (b) used the availa ble "diagnosis-type indicator." DESIGN. Analysis of existing administrative data. SETTING: Twenty-three Canadian hospitals. PATIENTS: A total of 50,357 coronary artery bypass graft surgery cases. MEASUREMENTS AND MAIN RESULTS: Among 21 clinical variables whose definition s involve the diagnosis-type indicator, 14 were predominantly (greater than or equal to 97%) baseline risk factors when present. Seven variables were often complication diagnoses: renal disease (when present, 13% coded as com plications), recent myocardial infarction (15%), peptic Weer disease (15%), congestive heart failure (17%), cerebrovascular disease (26%), hemiplegia (34%), and severe liver disease (35%). The results of risk adjustment analy ses predicting in-hospital mortality differed when the diagnosis-type indic ator was either used or ignored, and as a result, adjusted hospital mortali ty rates and rankings changed, often dramatically, with rankings increasing for 10 hospitals, decreasing for 9 hospitals, and remaining the same for o nly 4 hospitals. CONCLUSIONS: The results of analyses performed using the diagnosis-type ind icator in Canadian administrative data differ considerably from analyses th at ignore the indicator. The widespread introduction of such an indicator s hould be considered in other countries, because risk-adjustment analyses pe rformed without a diagnosis-type indicator may yield misleading results.