Troponin T and myoglobin at admission: value of early diagnosis of acute myocardial infarction

Abstract

We studied the predictive power at admission of troponin T and myoglobin and compared them with that of CK and CK-MB activity and ECG in 290 consecutive patients admitted for evaluation of a suspected AMI. The likelihood ratio for an ischaemic ECG at admission < 4 h (between 4 and 12 h) after onset of chest pain was 2.85 (1.92), for a inconclusive ECG 1.53 (1.98) and for a normal ECG 0.27 (0.35). In patients admitted < 4 h after onset of chest pain, the likelihood ratio for abnormal and normal myoglobin concentrations (8.06 and 0.67) was considerably better for detection of AMI as defined by the WHO criteria than for the other markers, including the ECG. In patients admitted 4-12 h after onset of chest pain, the likelihood ratios for abnormal and normal myoglobin concentrations were 4.88 and 0.42; for troponin T 3.11 and 0.31; for CK activity 3.44 and 0.49 and for CK-MB activity 4.08 and 0.54 respectively. The sensitivity for troponin T (64%) was better than that of the other markers but its specificity (74%) was worse, because in patients with unstable angina troponin T was frequently elevated (37%). Stepwise logistic regression analysis showed that the best predictors of AMI within 4 h after onset of chest pain were the ECG and myoglobin and between 4-12 h after onset of chest pain the ECG, CK-MB activity and myoglobin.