Diagnostic accuracy of myoglobin concentration for the early diagnosis of acute myocardial infarction

Study objective: We evaluated the diagnostic accuracy of myoglobin determin ation for the early diagnosis of acute myocardial infarction (AMI). Methods: Consecutive patients with chest pain were included in the study. R eceiver operating characteristic (ROC) analysis was used to assess optimal timing of blood sampling and cutoff values. Results: A total of 309 patients were included, of whom 162 patients had a diagnosis of AMI. ROC analysis revealed that the diagnostic accuracy of myo globin concentration as indicated by the area under the ROC curve (AUC) inc reased significantly from 3 (0.89+/-0.026) and 4 hours (0.93+/-0.019) to 5 hours after onset of symptoms (0.96+/-0.014; P=.0040 and .035, respectively ). At 5 hours (the earliest time point with maximal AUC), sensitivity was 8 7% and specificity was 97% using a myoglobin cutoff value of 90 mu g/L. Wit h a myoglobin cutoff value of 50 mu g/L, sensitivity was 95% (95% confidenc e interval 90% to 98%), but specificity was 86% (95% confidence interval 80 % to 93%). Conclusion: Myoglobin has maximal diagnostic accuracy for the diagnosis of AMI at 5 hours after the onset of symptoms, using a cutoff value of 50 mu g /L. In combination with the measurement of other biochemical markers, myogl obin determination could be particularly useful for triage of patients with AMI at an early stage.