title: Troponin-only Manchester Acute Coronary Syndromes (T-MACS) decision aid: single biomarker re-derivation and external validation in three cohorts.
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.
authors: Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, UK.|Emergency Department,Central Manchester University Hospitals Foundation NHS Trust, Manchester, UK.
authors: Richard
authors: R
authors: Body
authors: Emergency Department, North Bristol NHS Trust, Southmead Hospital, Bristol, UK.
authors: Edward
authors: http://orcid.org/0000-0002-2064-4618
authors: E
authors: Carlton
authors: Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, UK.
authors: Matthew
authors: M
authors: Sperrin
authors: Cardiology Department, Stockport NHS Foundation Trust, Stockport, UK.
authors: Philip S
authors: PS
authors: Lewis
authors: Biochemistry Department, Stockport NHS Foundation Trust, Stockport, UK.
authors: Gillian
authors: G
authors: Burrows
authors: Emergency Department,Central Manchester University Hospitals Foundation NHS Trust, Manchester, UK.|School of Healthcare Science, Manchester Metropolitan University, Manchester, UK.
authors: Simon
authors: S
authors: Carley
authors: Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, UK.|School of Healthcare Science, Manchester Metropolitan University, Manchester, UK.
authors: Garry
authors: G
authors: McDowell
authors: Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, UK.
authors: Iain
authors: I
authors: Buchan
authors: Department of Cardiology, Sunshine Coast Hospital and Health Services, University of the Sunshine Coast, Nambour, Australia.
authors: Kim
authors: K
authors: Greaves
authors: Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, UK.|Emergency Department,Central Manchester University Hospitals Foundation NHS Trust, Manchester, UK.|School of Healthcare Science, Manchester Metropolitan University, Manchester, UK.
authors: Kevin
authors: K
authors: Mackway-Jones
mesh_terms: D054058:Acute Coronary Syndrome / Q000175:diagnosis*; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000032:analysis / Q000097:blood; D015331:Cohort Studies; D003661:Decision Support Techniques; D004636:Emergency Service, Hospital / Q000458:organization & administration; D000074026:Fatty Acid Binding Protein 3 / Q000032:analysis / Q000097:blood; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D015995:Prevalence; D011446:Prospective Studies; D020107:Troponin T / Q000032:analysis* / Q000097:blood
chemical_list: D015415:Biomarkers; C493408:FABP3 protein, human; D000074026:Fatty Acid Binding Protein 3; D020107:Troponin T
keywords: acute myocardial infarct; cardiac care, diagnosis; diagnosis