• Tonje R Johannessen, Dan Atar, Odd Martin Vallersnes, Anne Cecilie K Larstorp, Ibrahimu Mdala, and Sigrun Halvorsen.
• Department of General Practice, University of Oslo, Oslo, Norway t.r.johannessen@medisin.uio.no.
• BMJ Open. 2021 Feb 24; 11 (2): e046024.

ObjectiveThis study aims to compare the rule-out safety of a single high-sensitivity cardiac troponin T (hs-cTnT) with the History, ECG, Age, Risk factors and Troponin (HEART) score in a low-prevalence primary care setting of acute myocardial infarction (AMI).ParticipantsPatients with non-specific symptoms suggestive of AMI were consecutively enroled at a primary care emergency clinic in Oslo, Norway from November 2016 to October 2018.MethodsAfter initial assessment by a general practitioner, hs-cTnT samples were drawn. AMI was ruled-out by a single hs-cTnT <5 ng/L measured ≥3 hours after symptom onset. The HEART score was calculated retrospectively; a score ≤3 of 10 points was considered low risk. We also calculated a modified HEART score using more sensitive hs-cTnT thresholds. The primary outcome was the diagnostic performance for the rule-out of AMI at the index event; the secondary the composite of AMI or all-cause death at 90 days.ResultsAmong 1711 patients, 61 (3.6%) were diagnosed with AMI, and 569 (33.3%) patients were assigned to single rule-out (<5 ng/L). With no AMIs in this group, the negative predictive value (NPV) and sensitivity were both 100.0% (95% CI 99.4% to 100.0% and 94.1% to 100.0%, respectively), and the specificity 34.5% (32.2% to 36.8%). The original HEART score triaged more patients as low risk (n=871), but missed five AMIs (NPV 99.4% (98.7% to 99.8%); sensitivity 91.8% (81.9% to 97.3%) and specificity 52.5% (50.0% to 54.9%)). The modified HEART score increased the low-risk sensitivity to 98.4% (91.2% to 100.0%), with specificity 38.7% (36.3% to 41.1%). The 90-day incidence of AMI or death in the single rule-out and the original and modified low-risk HEART groups were 0.0%, 0.7%, and 0.2%, respectively.ConclusionIn a primary care emergency setting, a single hs-cTnT strategy was superior to the HEART score in ruling out AMI. This rapid and safe approach may enhance the assessment of patients with chest pain outside of hospitals.Trial Registration NumberNCT02983123.© Author(s) (or their employer(s)) 2021. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.

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