Diagnostic Accuracy of a Novel Point of Care High‐Sensitivity Troponin Assay in the Prehospital Environment

OBJECTIVE: To evaluate the diagnostic accuracy of a novel point of care (POC) high-sensitivity troponin (hs-cTn) assay, used alone or incorporated within validated decision aids, for acute myocardial infarction (AMI) in the prehospital setting. METHODS: A pre-specified secondary analysis of the Prehospital Evaluation of Sensitive Troponin (PRESTO) prospective diagnostic accuracy study, conducted in four ambulance services and 12 Emergency Departments (EDs; February 2019-March 2020). Paramedics included consenting adults with suspected AMI and no other reason for conveyance. Clinical data and venous blood were collected at the scene, and samples conveyed to hospital with participants. Plasma samples were later analyzed for hs-cTn using a novel POC hs-cTn assay (Abbott Point of Care i-STAT hs-TnI). The target condition was an adjudicated index diagnosis of type 1 AMI. RESULTS: Of 817 consenting participants, 704 were eligible for inclusion in this analysis, with type 1 AMI occurring in 89 (12.6%). At the limit of detection (< 2 ng/L), POC hs-cTn had 100.0% sensitivity (95% CI 95 9%-100.0%) but only 4.6% specificity (95% CI 3.1%-6.5%). A Troponin-only Manchester Acute Coronary Syndromes (T-MACS) very-low risk outcome identified 134 (19.7%) patients for non-conveyance with 98.9% sensitivity (95% CI 94.9%-100.0%), 99.3% negative predictive value (NPV, 95% CI 95.0%-99.9%), and 22.5% specificity (95% CI 19.2%-26.1%). A low-risk modified HEART score identified 150 (22.0%) patients with 93.2% sensitivity (95% CI 85.8%-97.5%), 96.0% NPV (91.6%-98.1%), and 24.3% specificity (95% CI 20.9%-27.9%). In an exploratory analysis, hs-cTn < 5 ng/L identified 295 (41.9%) patients with 98.9% sensitivity (93.9%-100.0%), 99.7% NPV (97.7%-100.0%), and 47.8% specificity (95% CI 43.8%-51.8%). CONCLUSIONS: This novel POC hs-cTn assay achieves high sensitivity and NPV when used alongside the T-MACS decision aid, but efficiency may be greater at a 5 ng/L threshold without requiring any decision aid. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT03561051.