VALUE OF MYOGLOBIN, TROPONIN-T, AND CK-MB(MASS) IN RULING OUT AN ACUTE MYOCARDIAL-INFARCTION IN THE EMERGENCY ROOM

Background Ruling out acute myocardial infarction (AMI) on the basis o f rapid assays for cardiac markers will allow early triage of patients and cost-effective use of available coronary care facilities. Methods and Results We studied the value of myoglobin, creatine kinase (CK)-M B(mass) and troponin T in ruling out an AMI in the emergency room in 3 09 consecutive patients presenting with chest pain. The gold standard for AMI was the combination of history, EGG, and a typical curve of th e CK-MB activity (CK-MB(act)). Myoglobin was the earliest marker, and its negative predictive value (NPV) was significantly higher than for CK-MB(mass) and troponin T from 3 to 6 hours after the onset of sympto ms (myoglobin versus CKMB(mass) P<.03; myoglobin versus troponin T, P< .01). The NPV of myoglobin reached 89% 4 hours after the onset of symp toms. The NPV of CK-MB(mass) reached 95% 7 hours after the onset of sy mptoms. Troponin T was not an early marker for ruling out AMI, and NPV changed over time, together with CK-MB(act). The early NPV was higher in a subgroup of patients with a low probability of the presence of A MI for the three markers. Cardiac markers rise earlier in patients wit h large infarcts than in patients with small infarcts as indicated by the cumulative proportion of the marker above the upper reference limi t at each time point (myoglobin, P=.04; CK-MB(mass), P=.013; troponin T, P=.016). Conclusions For ruling out AMI in the emergency room, myog lobin is a better marker than CK-MB(mass) or troponin T from 3 until 6 hours after the onset of symptoms, but the maximal NPV reaches only 8 9%. At 7 hours, the NPV of CK-MB(mass) is 95%. The test characteristic s are influenced by the probability of the presence of AMI in the pati ents studied and by the size of their AMI. Infarct size of AMI patient s should be reported in studies evaluating cardiac markers.