CARDIAC MARKERS IN THE EARLY HOURS OF ACUTE MYOCARDIAL-INFARCTION - CLINICAL-PERFORMANCE OF CREATINE-KINASE, CREATINE-KINASE MB ISOENZYME (ACTIVITY AND MASS CONCENTRATION), CREATINE-KINASE MM AND MB SUBFORM RATIOS, MYOGLOBIN AND CARDIAC TROPONIN-T

We compared early markers of acute myocardial infarction (AMI) in the first 6 h from the onset of symptoms in 133 non-traumatized patients a rriving at the emergency department with chest pain suggestive of AMI. Clinical performance parameters were calculated on the basis of 45 pa tients with AMI and 88 patients with a non-AMI diagnosis. At admission and in the first 0-3 h after the onset of chest pain the creatine kin ase-MB (CK-MB) subform ratio was the most sensitive test at a comparab le specificity level of 0.95. In the time interval of 3-5 h, myoglobin , the CK-MB mass concentration and the CK-MB subform ratio were associ ated with the greatest areas under receiver operating characteristic ( ROC) curves, but differences between these tests were small and non-si gnificant. At 6 h from the onset of pain, differences in clinical perf ormance between the same three tests were even smaller whether or not samples drawn after the start of thrombolytic treatment were included in the test comparison. For confirmation of AMI at 6 h after onset of pain, CK-MB (activity and mass concentration) demonstrated the highest positive likelihood ratio, and for exclusion of AMI at 6 h the CK-MB subform ratio was associated with the highest negative likelihood rati o. However, differences between the CK-MB subform ratio, CK-MB mass co ncentration and myoglobin were not significant as estimated by the sub stantial overlap between the confidence intervals of the likelihood ra tios and the ROC areas at 6 h. Cardiac troponin T (cTnT) demonstrated an ROC area equal to the CK-MB isoform ratio and myoglobin at 6 h. How ever, the likelihood ratio for ruling out AMI was lower, mostly due to the elevated cTnT in unstable coronary disease not defined as AMI. We conclude that the CK-MB subform ratio, CK-MB mass concentration and m yoglobin do not demonstrate any significant differences in clinical pe rformance for ruling in or ruling out acute myocardial infarction at 6 h after the onset of chest pain.