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 beneficiaries who had an acute myocardial infarction (AMI) in 1987 and validate it on two national cohorts: (1) a cohort of 164,427 Medicare beneficiaries who had an AMI in 1988 and (2) a cohort of 10,466 patients admitted to Veterans Administration Hospitals (VAH) for AMI in 1988-1991. The impact of each sensitivity was expressed as; (1) the risk of mortality 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 calculated the area under an ROC curve obtained by fitting a logistic regression model to each validation population. The two year mortality rate for 30-day survivors was approximately 30% in each of the 3 cohorts. The 5 most prevlent comorbidities coded in the developmental cohort were heart failure (34%), chronic angina (27%), minor arrythmias (25%) and uncomplicated hypertension (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) resulted 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 prototype for others wishing to assess comorbidity in other targeted subgroups.
Normand
S L
SL
Department of Health Care polciy Harvard Medical School, Boston MA 02115.
Morris
C N
CN
Fung
K S
KS
McNeil
B J
BJ
Epstein
A M
AM
D000368:Aged; D000369:Aged, 80 and over; D015897:Comorbidity; D005260:Female; D006801:Humans; D007345:Insurance Claim Review; D016015:Logistic Models; D008297:Male; D006278:Medicare; D009203:Myocardial Infarction / Q000453:epidemiology / Q000401:mortality*; D012372:ROC Curve; D012307:Risk Factors; D014481:United States / Q000453:epidemiology