Creatine kinase isoenzymes. Predictive value in the early diagnosis of acute myocardial infarction.

This is a prospective study of the value of the creatine kinase (CK) isoenzyme determination in the early diagnosis of acute myocardial infarction. The presence or absence of the MB isoenzyme was correlated with electrocardiogram and standard enzymes. The frequency of falsely positive and falsely negative results for CK-MB, electrocardiogram and each standard enzyme was calculated and, using the elements of conditional probability theory, their predictive values for the diagnosis of acute myocardial infarction were determined. Results indicate that CK-MB combines the best attributes of the electrocardiogram and standard enzyme tests: detectable MB isoenzyme activity by acrylamide slab electrophoresis has a predictive value for the diagnosis if acute myocardial infarction comparable to that of a positive electrocardiogram; absence of MB isoenzyme activity, in the 24 hour period following the onset of symptoms, excludes the diagnosis of acute myocardial infarction with a probability equivalent to that provided by normal standard enzyme results.