FAILURE OF NEW BIOCHEMICAL MARKERS TO EXCLUDE ACUTE MYOCARDIAL-INFARCTION AT ADMISSION

In a substantial proportion of patients with suspected myocardial infa rction, biochemical markers are needed for clinical decision-making at the time of admission, because electrocardiographic (ECG) recordings are inconclusive. We have assessed the usefulness for exclusion of myo cardial infarction at admission of the newer markers creatine kinase M B (CK-MB) mass concentration, troponin T, and myoglobin in comparison with the routinely used markers creatine kinase (CK) and CK-MB activit y. 290 consecutive patients were enrolled. Acute myocardial infarction was diagnosed on the basis of clinical history, ECG criteria, and tim e-dependent changes in CK and CK-MB activity. 153 patients had definit e acute myocardial infarction. Troponin T had the highest sensitivity for prediction of acute myocardial infarction; high concentrations (ab ove the upper reference limits) were found in 98 (64%) of the patients with infarctions compared with 92 (60%) for CK-MB mass concentration, 76 (50%) for myoglobin, 61 (40%) for CK activity, and 53 (35%) for CK -MB activity. However, troponin T also had the highest ''false-positiv e'' rate; of 137 patients without myocardial infarction, 36 (26%) had high troponin T concentrations. Sensitivity, specificity, and positive and negative predictive values were calculated in relation to time be tween onset of chest pain and hospital admission. Although CK-MB mass concentration was, by a small margin, the best marker in patients admi tted within 8-10 h of onset of chest pain, all the markers had negativ e predictive values too low to allow exclusion of acute myocardial inf arction at admission in patients with symptoms suggestive of myocardia l infarction of less than 10 h duration.