Ruling out acute myocardial infarction in emergency primary care: The OUT-ACS study (One-hoUr Troponin in a low-prevalence population of Acute Coronary Syndrome)

Abstract

Chest pain is a frequent presenting symptom in emergency primary care, challenging due to the lack of sensitive diagnostic tools to exclude an acute myocardial infarction (AMI). The consequent clinical uncertainty contributes to high hospital referral rates of low-risk patients, congested emergency departments, and extensive use of healthcare resources and procedures of limited added value. The observational OUT-ACS (One-hoUr Troponin in a low-prevalence population of Acute Coronary Syndrome) study was conducted from 2016 to 2018 at a large emergency primary care clinic in Oslo, Norway. The aim was to investigate whether AMI could be excluded in low-risk patients using a 0/1-hour algorithm for high-sensitivity cardiac troponin T (hs-cTnT). AMI was adjudicated in 61 (3.6%) of 1711 patients. The patients were categorised as rule-out, rule-in or further observation by the algorithm, following the European Society of Cardiology guidelines. For patients assigned to the large AMI rule-out group (76.6 %), the algorithm achieved high safety at the index episode and had few events in the following 90 days. A total of 4% was assigned towards rule-in with a moderate AMI accuracy. The overall efficacy and safety of the algorithm were further improved by applying novel criteria for patients in the observation group. We also found that the rule-out performance of a single troponin measurement was superior to the HEART (History, ECG, Age, Risk factors and Troponin) score in our low-risk cohort. Finally, assessing low-risk patients with chest pain in emergency primary care was shown to be cost-effective, with €1794 saved per low-risk patient and a mean decrease in length of stay of 18.9 hours compared to routine hospital management. Based on our findings, the 0/1-hour algorithm appears safe, efficient, and cost-effective for assessing low-risk patients with chest pain in emergency primary care.