Performance characteristics of creatine kinase-MB isoenzyme measured with an immunoenzymometric and an immunoinhibition assay in acute myocardial infarction with and without thrombolytic therapy.

In a time study we compared the analytical and clinical performance of the Tandem Icon QSR CK-MB enzyme-immunoassay (Hybritech) (creatine kinase-MB) and a creatine kinase-MB immunoinhibition method (Boehringer Mannheim GmbH) (creatine kinase-B). Two hundred and ninety-nine serum samples from 38 patients suspected of acute myocardial infarction were collected at regular intervals during 48 hours. Twenty-nine patients were diagnosed as having acute myocardial infarction, of whom 19 received thrombolytic therapy. Although highly correlated, the large scatter around the regression line at low values indicated a different clinical performance of the two methods. We evaluated and compared test performance at different decision levels by means of frequency distributions and predictive values of positive and negative results. For early diagnosis of acute myocardial infarction (4 hours after onset of pain) the Hybritech creatine kinase-MB method gives acceptable predictive values. In thrombolytic treated acute myocardial infarction patients, the peak creatine kinase-MB and creatine kinase-B concentrations were reached after 13.0 h and 13.6 h after the onset of pain, compared with 19.8 h and 17.8 h for patients without thrombolytic therapy.