Objective To evaluate the accuracy of a 2-h serial multiple biomarker (SMB) protocol for exclusion of myocardial infarction (MI) in the Emergency Department.

Methods A prospective, multicentre, observational study enrolled patients undergoing evaluation for possible MI. Blood samples at presentation and 2 h later were analysed for myoglobin, creatinine kinase-MB, troponin-I and B-natriuretic peptide. Thrombolysis in Myocardial Infarction (TIMI) score and National Heart Foundation of Australia/Cardiac Society of Australia and New Zealand (NHF/CSANZ) guideline for acute coronary syndrome were used to determine clinical risk. Primary outcome was MI diagnosed at index presentation. Secondary outcome was composite of all-cause mortality, MI and previously unplanned coronary revascularisation within 30 days.

Results 1758 patients were recruited. 168 (11%) of 1501 with data sufficient for analysis had MI, and 223 (14%) of 1620 had a secondary outcome. SMB sensitivity and specificity were 0.90 (95% CI 0.84 to 0.94) and 0.41 (95% CI 0.39 to 0.44) for MI. For 30-day outcome, SMB sensitivity and specificity were 0.84 (95% CI 0.78 to 0.88) and 0.41 (95% CI 0.39 to 0.44), compared with standard 8–12 h troponin sensitivity and specificity of 0.79 (95% CI 0.73 to 0.84) and 0.96 (95% CI 0.95 to 0.97). Combined with risk scores, SMB had sensitivity and specificity for MI of 0.99 (0.96 to 1.00) and 0.11 (95% CI 0.09 to 0.12) for TIMI score 0, compared with 0.98 (95% CI 0.94 to 0.99) and 0.31 (95% CI 0.29 to 0.34) for NHF/CSANZ low/intermediate risk groups.

Conclusions SMB alone is not sufficiently sensitive to exclude MI. Combined with risk scoring, SMB appears to identify patients at lower risk. This requires prospective validation.