Validation of Rapid Rule‐Out Criteria Using the Beckman Access hsTnI Assay for Patients With Suspected Myocardial Infarction in a Cardiac Emergency Department

OBJECTIVE: To externally validate the current Monash Health criteria for rapid rule-out (RRO) of myocardial infarction (MI) at a tertiary cardiac emergency (CE). METHODS: All patients with suspected MI at the Victorian Heart Hospital (VHH) CE from April to June 2023 were eligible. Those with ST-elevation MI diagnosis from the initial ECG were excluded. The Monash Health RRO thresholds for the Access hsTnI laboratory high-sensitivity cardiac-troponin-I (hs-cTnI) assay are < 6 ng/L (females) or < 11 ng/L (males). The RRO criteria, derived at a general emergency department (ED) also require symptom onset > 2-h pre-hs-cTnI test and an ECG with no new ischaemic changes. MI diagnosis was determined by cardiologist-emergency physician consensus. The primary objective was the demonstration of RRO criteria performance in the VHH CE population, with sensitivity and negative predictive value (NPV) for index MI > 99%. Patient characteristics were also compared for those meeting RRO criteria or not. RESULTS: For the 1253 eligible patients, median age was 66 years [IQR: 53, 78] and 686 (54.7%) were male. Of the total, 334 (26.7%) met RRO criteria. The NPV for MI was 100% (95% CI: 98.9, 100.0), with sensitivity 100% (95% CI: 96.5, 100.0). Those meeting RRO criteria were younger (60 [IQR: 49, 72] vs. 68 [IQR: 56, 80] years) and less likely to be admitted (21.9% [95% CI: 17.5, 26.7] vs 49.6% [95% CI: 46.3, 52.9]). CONCLUSIONS: RRO criteria derived in a general ED population had a similarly high sensitivity and NPV for MI at a tertiary CE department. This supports external validity.