DEVELOPMENT AND VALIDATION OF A CLAIMS BASED INDEX FOR ADJUSTING FOR RISK OF MORTALITY - THE CASE OF ACUTE MYOCARDIAL-INFARCTION

We developed a comorbidity index on a cohort of 162,699 Medicare benef iciaries who had an acute myocardial infarction (AMI) in 1987 and vali dated it on two national cohorts: (1) a cohort of 164,427 Medicare ben eficiaries who had an AMI in 1988 and (2) a cohort of 10,466 patients admitted to Veterans Administration Hospitals (VAH) for AMI in 1988-19 91. The impact of each comorbidity was expressed as: (1) the risk of m ortality for those with the comorbidity, (2) the adjustment to the log odds for 2 year mortality and (3) the age-based likelihood of 2 year mortality. Models were validated by calculating the area under an ROC curve obtained by fitting a logistic regression model to each validati on population. The two year mortality rate for 30-day survivors was ap proximately 30% in each of the 3 cohorts. The 5 most prevalent comorbi dities coded in the developmental cohort were heart failure (34%), chr onic angina (27%), minor arrythmias (25%) and uncomplicated hypertensi on (18%). Cancer was the most powerful predictor of 2 year mortality, impacting mortality the same as a 18.3 year age increase. Saturation ( having all secondary diagnoses in the discharge summary filled) result ed in a 9.2 year age increase. Validation in the 1988 Medicare and in the Veterans Administration Hospitals cohorts resulted in areas of 73% and 72% under the respective ROC curves. Our methods can serve as a p rototype for others wishing to assess comorbidity in other targeted su bgroups.