Timed sequential analysis of creatine kinase in the diagnosis of myocardial infarction in patients over 65 years of age.

AIM: To assess the value of timed sequential analysis of creatine kinase (CK) activity for the early diagnosis of acute myocardial infarction (AMI) in patients over 65 years of age. METHOD: Samples were collected on admission and eight to 12 hours later from 156 patients over 65 years of age. Routine cardiac enzyme activities were determined and serial electrocardiograms (ECGs) recorded. The predictive value of timed samples for CK activity, standard cardiac enzyme activities, and ECGs was compared with the final diagnosis on discharge. RESULTS: Forty one patients had a discharge diagnosis of AMI, 83 of angina pectoris, and the remaining 32 patients had other diagnoses. Electrocardiograms had a sensitivity of 55% and a specificity of 96%, giving a predictive value of 86% for a negative and 84% for a positive ECG. Standard cardiac enzymes had a predictive value of 99% for a negative result but only 68% for a positive result. The logarithm of the rate of change of CK activity had a predictive value of 97% for a negative result and 95% for a positive result. CONCLUSION: This study has shown that slope analysis of CK activity can be used for the early diagnosis of AMI in patients over 65 years of age, and that this was not affected by the presence of possible confounding diagnoses.