Risk adjustment using administrative data: impact of a diagnosis-type indicator.
OBJECTIVE
To determine the frequency with which commonly coded clinical variables are complications, as opposed to baseline comorbidities, and to compare the results of 2 risk-adjusted outcome analyses for coronary artery bypass graft surgery for which we either (a) ignored, or (b) used the available "diagnosis-type indicator."


METHODS
Analysis of existing administrative data.


METHODS
Twenty-three Canadian hospitals.


METHODS
A total of 50,357 coronary artery bypass graft surgery cases.


RESULTS
Among 21 clinical variables whose definitions involve the diagnosis-type indicator, 14 were predominantly (> or =97%) baseline risk factors when present. Seven variables were often complication diagnoses: renal disease (when present, 13% coded as complications), recent myocardial infarction (15%), peptic ulcer disease (15%), congestive heart failure (17%), cerebrovascular disease (26%), hemiplegia (34%), and severe liver disease (35%). The results of risk adjustment analyses predicting in-hospital mortality differed when the diagnosis-type indicator was either used or ignored, and as a result, adjusted hospital mortality rates and rankings changed, often dramatically, with rankings increasing for 10 hospitals, decreasing for 9 hospitals, and remaining the same for only 4 hospitals.


CONCLUSIONS
The results of analyses performed using the diagnosis-type indicator in Canadian administrative data differ considerably from analyses that ignore the indicator. The widespread introduction of such an indicator should be considered in other countries, because risk-adjustment analyses performed without a diagnosis-type indicator may yield misleading results.
Ghali
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Department of Medicine, Faculty of Medicine, University of Calgary, Calgary, Alberta, Canada. wghali@ucalgary.ca
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D002170:Canada; D015897:Comorbidity; D001026:Coronary Artery Bypass / Q000009:adverse effects*; D005260:Female; D017052:Hospital Mortality; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D017063:Outcome Assessment, Health Care / Q000379:methods*; D020379:Risk Adjustment