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Troponin-only Manchester Acute Coronary Syndromes (T-MACS) decision aid: single biomarker re-derivation and external validation in three cohorts
  1. Richard Body1,2,
  2. Edward Carlton3,
  3. Matthew Sperrin1,
  4. Philip S Lewis4,
  5. Gillian Burrows5,
  6. Simon Carley2,6,
  7. Garry McDowell1,6,
  8. Iain Buchan1,
  9. Kim Greaves7,
  10. Kevin Mackway-Jones1,2,6
  1. 1Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, UK
  2. 2Emergency Department,Central Manchester University Hospitals Foundation NHS Trust, Manchester, UK
  3. 3Emergency Department, North Bristol NHS Trust, Southmead Hospital, Bristol, UK
  4. 4Cardiology Department, Stockport NHS Foundation Trust, Stockport, UK
  5. 5Biochemistry Department, Stockport NHS Foundation Trust, Stockport, UK
  6. 6School of Healthcare Science, Manchester Metropolitan University, Manchester, UK
  7. 7Department of Cardiology, Sunshine Coast Hospital and Health Services, University of the Sunshine Coast, Nambour, Australia
  1. Correspondence to Dr Richard Body, Emergency Department, Manchester Royal Infirmary, Oxford Road, Manchester M13 9WL, UK; richard.body{at}manchester.ac.uk

Abstract

Background The original Manchester Acute Coronary Syndromes model (MACS) ‘rules in’ and ‘rules out’ acute coronary syndromes (ACS) using high sensitivity cardiac troponin T (hs-cTnT) and heart-type fatty acid binding protein (H-FABP) measured at admission. The latter is not always available. We aimed to refine and validate MACS as Troponin-only Manchester Acute Coronary Syndromes (T-MACS), cutting down the biomarkers to just hs-cTnT.

Methods We present secondary analyses from four prospective diagnostic cohort studies including patients presenting to the ED with suspected ACS. Data were collected and hs-cTnT measured on arrival. The primary outcome was ACS, defined as prevalent acute myocardial infarction (AMI) or incident death, AMI or coronary revascularisation within 30 days. T-MACS was built in one cohort (derivation set) and validated in three external cohorts (validation set).

Results At the ‘rule out’ threshold, in the derivation set (n=703), T-MACS had 99.3% (95% CI 97.3% to 99.9%) negative predictive value (NPV) and 98.7% (95.3%–99.8%) sensitivity for ACS, ‘ruling out’ 37.7% patients (specificity 47.6%, positive predictive value (PPV) 34.0%). In the validation set (n=1459), T-MACS had 99.3% (98.3%–99.8%) NPV and 98.1% (95.2%–99.5%) sensitivity, ‘ruling out’ 40.4% (n=590) patients (specificity 47.0%, PPV 23.9%). T-MACS would ‘rule in’ 10.1% and 4.7% patients in the respective sets, of which 100.0% and 91.3% had ACS. C-statistics for the original and refined rules were similar (T-MACS 0.91 vs MACS 0.90 on validation).

Conclusions T-MACS could ‘rule out’ ACS in 40% of patients, while ‘ruling in’ 5% at highest risk using a single hs-cTnT measurement on arrival. As a clinical decision aid, T-MACS could therefore help to conserve healthcare resources.

  • acute myocardial infarct
  • diagnosis
  • cardiac care, diagnosis

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