Pre-hospital One-Hour Troponin in a Low-Prevalence Population of Acute Coronary Syndrome: OUT-ACS study

Abstract

Objective: The European Society of Cardiology 0/1-hour algorithm for high-sensitivity cardiac troponin T (hs-cTnT) has demonstrated high rule-out safety in large hospital validation cohorts. We aimed to validate the algorithm in a primary care setting, where patients have a lower pretest probability for acute coronary syndrome.

Methods: This prospective, observational, diagnostic study included patients with acute non-specific chest pain admitted to a primary care emergency clinic in Oslo, Norway, from November 2016 to October 2018. hs-cTnT was measured after 0, 1 and 4 hours. The primary outcome measure was the diagnostic performance of the 0/1-hour algorithm, the 90-day incidence of AMI or all-cause death the secondary.

Results: Among 1711 included patients, 61 (3.6%) were diagnosed with AMI. By applying the algorithm, 1311 (76.6%) patients were assigned to the rule-out group. The negative predictive value was 99.9% (95% CI 99.5% to 100.0%), the sensitivity and specificity 98.4% (91.2-100.0) and 79.4% (77.4-81.3), respectively. Sixty-six (3.9%) patients were triaged towards rule-in, where 45 were diagnosed with AMI. The corresponding positive predictive value was 68.2% (58.3-76.7), sensitivity 73.8% (60.9-84.2), and specificity 98.7% (98.1-99.2). Among 334 (19.5%) patients assigned to the observation group in need of further tests, 15 patients had an AMI. The following 90 days, five new patients experienced an AMI and nine patients died, with a low incidence in the rule-out group (0.3%).

Conclusion: The 0/1-hour algorithm for hs-cTnT seems safe, efficient and applicable for an accelerated assessment of patients with non-specific chest pain in a primary care emergency setting.

Trial registration number: NCT02983123.

Keywords: acute coronary syndrome; cardiovascular examination; general practice; myocardial ischaemia and infarction (IHD); primary care.

Conflict of interest statement

Competing interests: DA has received speaker’s honoraria and consultancy fees from Amgen, Astra Zeneca, Bayer Healthcare, BMS, Boehringer-Ingelheim, Merck, Novartis, Pfizer and Sanofi-Aventis, and research grants from the institution by Medtronic and BMS. SH has received speaker’s honoraria and consultancy fees from Amgen, Astra Zeneca, Bayer Healthcare, BMS, Boehringer-Ingelheim, Merck, Novartis, Pfizer and Sanofi-Aventis, and has no conflicts in relation to this study.

© Author(s) (or their employer(s)) 2020. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.

Figures

Figure 1

Patient flow diagram. Management of acute chest pain at the OAEOC and patient flowchart during the study. *, critically ill patients are directly hospitalised by the ambulance services. ACS, acute coronary syndrome; AMI, acute myocardial infarction; hs-cTnT, high-sensitivity cardiac troponin T; OAEOC, Oslo Accident and Emergency Outpatient Clinic.

Figure 2

Prehospital validation of the ESC 0/1-hour algorithm. The patients were assigned to rule-out, rule-in or the observation group according to the baseline hs-cTnT value or the 0–1 hour absolute change,where high safety is demonstrated in the rule-out group. Summary of the calculations with corresponding 95 % CI are presented at the bottom. *, given a >3-hour symptom onset before the first hs-cTnT sample; †, rule-in and observation group combined; ǂ, rule-out and observation group combined. AMI, acute myocardial infarction; ESC, European Society of Cardiology; LR, likelihood ratio; hs-cTnT, high-sensitivity cardiac troponin T; NPV, negative predictive value; PPV, positive predictive value.

Figure 3

Overall diagnostic accuracy of the 0/1-hour algorithm for hs-cTnT. The overall diagnostic accuracy for AMI during the index episode was demonstrated by the area under the ROC curve at 96.0% (95 % CI 0.94% to 0.98%). The AUC was achieved by using two cut-off values to include the observation group: (1) rule-in: sensitivity 45/61=0.74 and specificity (1310+319)/1650=0.99, (2) rule-out: sensitivity (15+45)/61=0.98 and specificity: 1310/1650=0.79. AMI, acute myocardial infarction; AUC, area under the curve; hs-cTnT, high-sensitivity cardiac troponin T; ROC, receiver operating characteristic.