Abstract 14211: Positive Predictive Value of Troponin for NSTEMI Based on Chief Complaint

Introduction: Serum troponin is a ubiquitous biomarker used to diagnose acute myocardial infarction (AMI). The positive predictive value (PPV) of high-sensitivity troponin for Type 1 Myocardial Infarction is approximately 15% in the United States, compared with 55% in Europe, a difference that may be explained by differences in patient selection for testing. Our objective was to examine test characteristics for contemporary troponin assays based on chief complaint in the Emergency Department (ED). Methods: In a retrospective cohort analysis, we examined all 30,833 encounters in which a troponin test was performed in any of the 14 emergency departments within a large integrated health system between 10/1/18 and 10/1/19. All hospitals used a contemporary cardiac troponin-I (cTnI) assay. We excluded patients with ST-segment elevation myocardial infarction (STEMI) since this diagnosis is made by electrocardiogram. We grouped patients by chief complaint (CC) and further stratified by pre-specified cTnI thresholds. Within each cTnI/CC category, we calculated the proportion of patients subsequently classified with a principal ICD-10 diagnosis of non-STEMI (NSTEMI). Results: For all patients selected for cTnI testing, 1.7% were diagnosed with NSTEMI. Overall, the PPV of cTnI for NSTEMI was 11%. This PPV for NSTEMI was highest among patients with chest pain (33%). Excluding patients with chest pain, the PPV for NSTEMI was 3.9%. For nearly all chief complaints, the PPV for NSTEMI increased with higher cTnI thresholds. Conclusion: In a large integrated health system, fewer than one in fifty patients undergoing cTnI testing in the ED were ultimately diagnosed with NSTEMI. The PPV of cTnI for NSTEMI was significantly higher among patients presenting with chest pain compared to other chief complaints. These data highlight the importance of selecting patients for testing and interpreting abnormalities in the context of presenting symptoms.