Single vs Serial Measurements of Cardiac Troponin Level in the Evaluation of Patients in the Emergency Department With Suspected Acute Myocardial Infarction

IMPORTANCE: Chest pain is among the most common reasons for emergency department (ED) presentations. However, most patients are at low risk for acute coronary syndrome (ACS), with low cardiac adverse outcomes rates. Biomarker testing with troponin levels is key in the initial assessment for ACS. Although serial troponin testing can improve the diagnosis of ACS in clinical practice, some patients deemed to be low risk are discharged after a single negative troponin test result. OBJECTIVE: To report the clinical outcomes of patients discharged after a single negative troponin test result compared with patients discharged after serial troponin measurements. DESIGN, SETTING, AND PARTICIPANTS: This is a retrospective cohort study of ED encounters from May 5, 2016, to December 1, 2017, across 15 community EDs within an integrated health care system in southern California. The study cohort includes 27 918 adult ED encounters in which patients were evaluated for suspected ACS with a HEART (history, electrocardiogram, age, risk factors, and troponin) score and an initial conventional troponin-I measurement below the level of detection (<0.02 ng/mL). Statistical analysis was performed from December 1, 2019, to December 1, 2020. EXPOSURE: Single troponin test vs multiple troponin tests. MAIN OUTCOMES AND MEASURES: The primary outcome was acute myocardial infarction or cardiac mortality; secondary outcomes included coronary artery bypass graft, percutaneous coronary intervention, invasive coronary angiography, and unstable angina within 30 days of discharge. A multivariable logistic regression model was performed to evaluate the association between testing strategies and clinical outcomes. RESULTS: A total of 27 918 patient encounters (16 212 women [58.1%]; mean [SD] age, 58.7 [15.2] years) were included in the study. Of patients with an initial troponin measurement below the level of detection, 14 459 (51.8%) were discharged after a single troponin measurement, and 13 459 (48.2%) underwent serial troponin tests. After adjustment for cardiac risk factors and comorbidities, there was no statistically significant difference in the primary outcome of acute myocardial infarction or cardiac mortality within 30 days between the 2 groups (single troponin, 56 [0.4%] vs serial troponin, 52 [0.4%]; adjusted odds ratio, 1.41 [95% CI, 0.96-2.07]). Patients discharged after a single troponin test had lower rates of coronary artery bypass graft (adjusted odds ratio, 0.24 [95% CI, 0.11-0.48]) and invasive coronary angiography (adjusted odds ratio, 0.46 [95% CI, 0.38-0.56]). CONCLUSIONS AND RELEVANCE: This study suggests that patients are routinely discharged from the ED after a single negative troponin test result, and when compared with serial troponin testing, a single troponin test appears safe based on current physician decision-making, with no difference in rates of 30-day cardiac mortality and acute myocardial infarction, which are low in both groups.