Diagnostic accuracy of a point-of-care troponin i assay for acute myocardial infarction within 3 hours after presentation in early presenters to the emergency department with chest pain

Background: Guidelines recommend that serial cardiac marker testing to rule out acute myocardial infarction (AMI) be performed for 8 to 12 hours after symptom onset. We aim to determine the diagnostic accuracy of a contemporary point-of-care (POC) troponin I (TnI) assay within 3 hours for patients presenting within 8 hours of symptom onset. Methods: The MIDAS study collected blood from patients presenting with suspected acute coronary syndrome at presentation and at 90 minutes, 3 hours, and 6 hours in whom the emergency physician planned an objective cardiac ischemia evaluation. Criterion standard diagnoses were adjudicated by experienced clinicians using all available medical records per American Heart Association/American College of Cardiology criteria. Reviewers were blinded to the investigational marker, Cardio3 TnI POC. The Cardio3 TnI reference value was defined as >0.05 ng/mL. Measures of diagnostic accuracy are presented with 95% CI. Results: A total of 858 of 1107 patients met the inclusion criteria. The study cohort had 476 men (55.5%) with median age of 57.0 years (interquartile range 48.0-67.0 years). Median time from symptom onset to initial blood draw was 3.9 hours (interquartile range 2.7-5.2 hours). Acute myocardial infarction was diagnosed in 82 patients (9.6%). The sensitivity, specificity, positive likelihood ratio, and negative likelihood ratio over 3 hours were 84.1, 93.4, 12.8, and 0.17, respectively. There was no significant improvement in diagnostic accuracy associated with adding 6-hour serial testing to the 3-hour sample. Conclusion: In suspected patients with acute coronary syndrome presenting to the emergency department within 8 hours of symptom onset, 3 hours of serial testing with the Cardio3 TnI POC platform provides similar diagnostic accuracy for AMI as longer periods.