Background The Manchester Acute Coronary Syndromes (MACS) rule and the Troponin-only MACS (T-MACS) rule risk stratify patients with suspected acute coronary syndrome (ACS). This observational study sought to validate and compare the MACS and T-MACS rules for assessment of acute myocardial infarction (AMI).
Methods Prospectively collected data from twoEDs in Australia and New Zealand were analysed. Patients were assigned a probability of ACS based on the MACS and T-MACS rules, incorporating high-sensitivity troponin T, heart-type fatty acid-binding protein, ECG results and clinical symptoms. Patients were then deemed very low risk, low risk, intermediate or high risk if their MACS probability was less than 2%, between 2% and 5%, between 5% and 95% and greater than 95%, respectively. The primary endpoint was 30-day diagnosis of AMI. The secondary endpoint was 30-day major adverse cardiac event (MACE) including AMI, revascularisation or coronary stenosis (>70%). Sensitivity, specificity and predictive values were calculated to assess the accuracy of the MACS and T-MACS rules.
Results Of the 1244 patients, 114 (9.2%) were diagnosed with AMI and 163 (13.1%) with MACE. The MACS and T-MACS rules categorised 133 (10.7%) and 246 (19.8%) patients, respectively, as very low risk and potentially suitable for early discharge from the ED. There was one false negative case for both rules making sensitivity 99.1% (95.2%–100%).
Conclusions MACS and T-MACS accurately risk stratify very low risk patients. The T-MACS rule would allow for more patients to be discharged early. The potential for missed MACE events means that further outpatient testing for coronary artery disease may be required for patients identified as very low risk.
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Funding This study was supported by Emergency Medicine Foundation.
Competing interests WP is a consultant for Hospira/Pfizer outside the submitted work. JY has received postdoctoral research funding from the Lottery Health Board for studies investigating novel diagnostic and prognostic markers of cardiovascular disease. MT reports personal fees from Abbott and Roche, grants from Abbott, Alere and Beckman, personal fees and other from Alere
and Beckman, all outside the submitted work. CH reports personal fees from Astra Zeneca, Amgen, Bayer Healthcare, Boehringer Ingelheim, The Medicines Company and Medtronic, all outside the submitted work. LC reports grants from Roche; grants, consultancy fees and personal fees from Abbott Diagnostics; grants and consultancy fess from Siemens; grants from Radiometer; personal fees from AstraZeneca and personal fees from Novartis, all outside of the submitted work. JHG, RN, SD and JWP report no competing interests.
Provenance and peer review Not commissioned; externally peer reviewed.
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