Strategies for the early diagnosis of acute myocardial infarction using biochemical markers

We evaluated different diagnostic strategies for the early diagnosis of acute myocardial infarction, combining sensitivity and specificity of different markers evaluated singly and using combination testing in parallel and serial modes. Myoglobin, cardiac troponin I (TnI), creatine kinase (CK), and CK-MB mass were tested in blood samples from 26 patients with acute myocardial infarction collected at admission (T0; mean = 3.3 hours from the onset of chest pain) and 3 and 6 hours later. The comparison group was made up of 70 patients with renal failure, skeletal muscle diseases, stable angina, unstable angina, and chest pain of nonischemic origin. Single tests showed different sensitivities in relation to the different release kinetics; myoglobin was the most sensitive (69% at T0) although less specific (46%), and TnI showed the highest specificity (90%) and a sensitivity of 54%. Combination testing in a parallel mode using myoglobin and TnI or CK-MB had the same sensitivity and specificity as myoglobin tested singly. The best combination in a serial mode is myoglobin and TnI (at T0 sensitivity, 54%; specificity, 98%), as confirmed by the analysis of the positive predictive value, the negative predictive value, and the accuracy evaluated as a function of different disease prevalences.