Ninety-Minute Exclusion of Acute Myocardial Infarction By Use of Quantitative Point-of-Care Testing of Myoglobin and Troponin I

Background Diagnostic strategies with ECG and serum cardiac markers have been used to rule out acute myocardial infarction in 6 to 12 hours. The present study evaluated whether a multimarker strategy that used point-of-care measurement of myoglobin, creatine kinase (CK)-MB, and troponin I could exclude acute myocardial infarction in ≤3 hours. Methods and Results We prospectively enrolled consecutive patients (n=817) in the emergency department who were evaluated for possible acute myocardial infarction. In patients with nondiagnostic ECGs, we measured CK-MB, troponin I, and myoglobin with a point-of-care device at presentation and at 90 minutes, 3 hours, and 9 hours. Standard central laboratory testing of CK-MB was done at the same time intervals, and triage decisions were made by emergency physicians who were unaware of point-of-care results. Sensitivity and negative predictive value were compared for both the multimarker, point-of-care approach and the central laboratory strategy. Sensitivity and negative predictive value for point-of-care combination of myoglobin and troponin I by 90 minutes was 96.9% and 99.6%, respectively. CK-MB measurements and blood sampling at 3 hours did not improve sensitivity or negative predictive value. Median time from sampling to reporting of results was 71.0 minutes for the central laboratory versus 24.0 minutes for the point-of-care device ( P <0.001). Conclusions Acute myocardial infarction can be excluded rapidly in the emergency department by use of point-of-care measurements of myoglobin and troponin I during the first 90 minutes after presentation.