Validation of the (Troponin-only) Manchester Acute Coronary Syndromes decision aid with a contemporary cardiac troponin I assay

OBJECTIVES: The Manchester Acute Coronary Syndromes (MACS) decision aid can 'rules in' and 'rule out' acute coronary syndromes (ACS) by combining a patient's symptoms with the results of a single blood test taken at the time of arrival in the Emergency Department (ED). The original model (MACS) included two biomarkers: high sensitivity cardiac troponin T (hs-cTnT) and heart-type fatty acid binding protein (h-FABP). A refined model without h-FABP was found to have comparable sensitivity but greater specificity. We sought to validate MACS and T-MACS using the contemporary Siemens Advia Centaur cardiac troponin I assay to increase usability in practice.

METHODS: This is a secondary analysis from a prospective diagnostic cohort study at Stepping Hill Hospital, United Kingdom. Patients presenting with chest pain of suspected cardiac nature warranting rule out for ACS were included. All patients underwent hs-cTnT testing at least 12h after peak symptoms. The primary outcome was a diagnosis of ACS, defined as either prevalent acute myocardial infarction (AMI) or incident major adverse cardiac events (death, AMI or coronary revascularization) within 30days.

RESULTS: Of 405 included patients, 76 (18.8%) had ACS. MACS and T-MACS had similar C-statistics (0.94 for each, p=0.36) and sensitivity (difference 1.3%, 95% CI -1.3 to 3.9%, p=1.00) but T-MACS had significantly greater specificity (difference 16.7%, 95% CI 14.6-18.9%, p<0.0001). T-MACS and MACS would have allowed 36.3% and 22.5% patients to be immediately discharged respectively. Of patients classified as 'very low risk', none had ACS when MACS was used compared to one (0.7%) with T-MACS.

CONCLUSION: Both MACS and T-MACS effectively ruled out ACS even with a contemporary troponin I assay and could be used to reduce unnecessary hospital admissions.