OBJECTIVES: Current practice for suspected acute coronary syndrome (ACS) involves troponin testing 10-12 hours after symptom onset to diagnose myocardial infarction (MI). We aimed to estimate the diagnostic accuracy of early biomarkers for MI to determine if an earlier, accurate decision was possible. METHODS: A systematic review of all diagnostic cohort studies of patients presenting with suspected ACS comparing the following biomarkers at presentation with a reference standard based on the Universal definition of MI (troponin at 10-12 hours): early troponin I and T; Heart-type Fatty Acid Binding Protein (HFABP); ischaemia modified albumen (IMA) and myoglobin. A systematic search was undertaken of 10 electronic databases, citation lists and expert contacts, to identify relevant studies. The study selection, data extraction and quality assessment decisions were all verified by more than one reviewer. citations retrieved were divided between two reviewers (CC, SG) and screened for relevance to the review. Any discrepancies were resolved by discussion and reference to the full paper. Risk of bias was assessed using the Quality Assessment of Diagnostic Accuracy Studies (QUADAS) tool. Meta-analysis was conducted using Bayesian Markov chain Monte Carlo simulation. RESULTS: Compared with the Universal definition of MI, sensitivity and specificity (95% predictive interval) were 77% (29-96%) and 93% (46-100%) for troponin I; 80% (33-97%) and 91% (53-99%) for troponin T (99th percentile threshold); 81% (50-95%) and 80% (26-98%) for quantitative HFABP, 68% (11-97%) and 92% (20-100%) for qualitative HFABP; 77% (19-98%) and 39% (2-95%) for IMA and 62% (35-83%) and 83% (35-98%) for myoglobin. CONCLUSIONS: Early troponin I and T and H-FABP have modest sensitivity and specificity for MI at presentation, when compared with the gold standard, but estimates are subject to substantial uncertainty and primary data are subject to substantial heterogeneity. More research on high sensitivity troponin assays at presentation is required.