COMBINATION (MULTIPLE) TESTING FOR MYOCARDIAL-INFARCTION USING MYOGLOBIN, CREATINE KINASE-2 (MASS), AND TROPONIN-T

We retrospectively determined the mass concentrations of myoglobin, cr eatine kinase-2 (CK-2), and troponin T in serial samples from 80 patie nts with confirmed myocardial infarction (MI) and 60 non-MI patients. Results from receiver operating characteristic curve analyses show tha t all three tests are comparable in their diagnostic utility within th e first 12 h of infarction. Decision thresholds were selected at a con stant 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 sympt oms. 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 combi nation. Our results from combination testing indicate that for the ear ly diagnosis of MI, a single serum myoglobin measurement has diagnosti c 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. S erum troponin T is diagnostically similar to CK-2 (mass), although it has superior cardiac-tissue specificity, but it is not as yet commerci ally available as a ''stat'' test. Therefore, we recommend using tropo nin T as a confirmatory test 9 h after the onset of MI. Based on our f indings, we suggest a testing algorithm for the early biochemical diag nosis of MI.