A Measure of Mortality Risk for Elderly Patients with Acute Myocardial Infarction

The objective of this study was to derive and validate a simple scoring system that predicts risk of short-term mortality in elderly patients hospitalized with acute myocardial infarction (AMI) and to compare this derived score with the MedisGroups admission severity score. A myocardial infarction severity score (MISS) was derived from a database of clinical infor mation abstracted using MedisGroups and follow-up information on 30-day mortality status. The MISS was validated and compared with the MedisGroups Admission Severity Groups (ASGs) in a separate database. The derivation set included 2,037 Medicare patients 65 years old or older with confirmed AMI who were randomly selected from patients discharged from hospitals in seven states during 1985. The validation set consisted of 6,323 patients from the 1988 MedisGroups comparative database who were at least 65 years of age and had confirmed AMI. Multivariate logistic regression analysis found a set of nine abnormal patient characteristics that independently predict 30-day mortality. There was good agree ment between mortality rates predicted by the logistic model and observed mortality rates in the validation population. This regression model was then simplified to an additive score where eight of the characteristics were weighted as one point and one characteristic was weighted as two points. The MISS is the sum of the points for each patient. In the validation dataset, the 1,373 patients with the lowest MISS scores had a mortality rate of 4.6% and the 400 patients with the highest MISS scores had a mortality rate of 64%. In the same sample, using many more items of information, mortality rates were 3.5% for the 202 patients in the two lowest ASGs and 68% for the 154 patients in the highest ASGs. The authors conclude that the statistically derived MISS has better predictive power than MedisGroups ASG scores derived by expert opinion. MISS greatly simplifies the stratification into mortality- risk groups of elderly AMI patients. Key words: myocardial infarction severity score; predic tion ; mortality risk. (Med Decis Making 1993;13:152-160)