OBJECTIVESConcentrations of troponin measured with high sensitivity troponin assays are raised in a number of emergency department (ED) patients; however many are not diagnosed with acute myocardial infarction (AMI). Clinical comparisons between the early use (2h after presentation) of high sensitivity cardiac troponin T (hs-cTnT) and I (hs-cTnI) assays for the diagnosis of AMI have not been reported.DESIGN AND METHODSEarly (0 h and 2 h) hs-cTnT and hs-cTnI assay results in 1571 ED patients with potential acute coronary syndrome (ACS) without ST elevation on electrocardiograph (ECG) were evaluated. The primary outcome was diagnosis of index AMI adjudicated by cardiologists using the local cTnI assay results taken ≥6 h after presentation, ECGs and clinical information. Stored samples were later analysed with hs-cTnT and hs-cTnI assays.RESULTSThe ROC analysis for AMI (204 patients; 13.0%) for hs-cTnT and hs-cTnI after 2h was 0.95 (95% CI: 0.94-0.97) and 0.98 (95% CI: 0.97-0.99) respectively. The sensitivity, specificity, PLR, and NLR of hs-cTnT and hs-cTnI for AMI after 2h were 94.1% (95% CI: 90.0-96.6) and 95.6% (95% CI: 91.8-97.7), 79.0% (95% CI: 76.8-81.1) and 92.5% (95% CI: 90.9-93.7), 4.48 (95% CI: 4.02-5.00) and 12.86 (95% CI: 10.51-15.31), and 0.07 (95% CI: 0.04-0.13) and 0.05 (95% CI:0.03-0.09) respectively.CONCLUSIONSExclusion of AMI 2h after presentation in emergency patients with possible ACS can be achieved using hs-cTnT or hs-cTnI assays. Significant differences in specificity of these assays are relevant and if using the hs-cTnT assay, further clinical assessment in a larger proportion of patients would be required.