Combination (multiple) testing for myocardial infarction using myoglobin, creatine kinase-2 (mass), and troponin T

We retrospectively determined the mass concentrations of myoglobin, creatine kinase-2 (CK-2), and troponin T in serial samples from 80 patients with confirmed myocardial infarction (MI) and 60 non-MI patients. Results from receiver operating characteristic curve analyses show that all three tests are comparable in their diagnostic utility within the first 12 h of infarction. Decision thresholds were selected at a constant rule-in specificity of 95% and rule-out sensitivities of 95% at, respectively, 3-6, 6-9, and 9-12 h intervals after the onset of symptoms. Test sensitivities and specificities were compared for each, used as: a single test; two-test parallel combination; three-test parallel combination; two-test series combination; and three-test series combination. Our results from combination testing indicate what for the early diagnosis of MI, a single serum myoglobin measurement has diagnostic utility at 3 h after the onset of symptoms, and myoglobin and CK-2 (mass) in combination later than 3 h following the onset of symptoms. Serum troponin T is diagnostically similar to CK-2 (mass), although it has superior cardiac-tissue specificity, but it is not as yet commercially available as a "stat" test. Therefore, we recommend using troponin T as a confirmatory test 9 h after the onset of MI. Based on our findings, we suggest a testing algorithm for the early biochemical diagnosis of MI.