title: Implications of lowering threshold of plasma troponin concentration in diagnosis of myocardial infarction: cohort study.
abstract: OBJECTIVE
  To assess the relation between troponin concentration, assay precision, and clinical outcomes in patients with suspected acute coronary syndrome.
  
  
  METHODS
  Cohort study.
  
  
  METHODS
  Tertiary centre in Scotland.
  
  
  METHODS
  2092 consecutive patients admitted with suspected acute coronary syndrome were stratified with a sensitive troponin I assay into three groups (<0.012, 0.012-0.049, and ≥0.050 µg/L) based on the 99th centile for troponin concentration (0.012 µg/L; coefficient of variation 20.8%) and the diagnostic threshold (0.050 µg/L; 7.2%).
  
  
  METHODS
  One year survival without events (recurrent myocardial infarction, death) in patients grouped by troponin concentration.
  
  
  RESULTS
  Troponin I concentrations were <0.012 µg/L in 988 patients (47%), 0.012-0.049 µg/L in 352 patients (17%), and ≥0.050 µg/L in 752 patients (36%). Adoption of the 99th centile would increase the number of people receiving a diagnosis of myocardial infarction from 752 to 1104: a relative increase of 47%. At one year, patients with troponin concentrations of 0.012-0.049 µg/L were more likely to be dead or readmitted with recurrent myocardial infarction than those with troponin concentrations <0.012 µg/L (13% v 3%, P<0.001; odds ratio 4.7, 95% confidence interval 2.9 to 7.9). Compared with troponin ≥0.050 µg/L, patients with troponin 0.012-0.049 µg/L had a higher risk profile but were less likely to have a diagnosis of, or be investigated and treated for, acute coronary syndrome.
  
  
  CONCLUSIONS
  Lowering the diagnostic threshold to the 99th centile and accepting greater assay imprecision would identify more patients with acute coronary syndrome at risk of recurrent myocardial infarction and death but would increase the diagnosis of myocardial infarction by 47%. It remains to be established whether reclassification of these patients and treatment for myocardial infarction would improve outcome.
authors.affiliation: BHF/University Centre for Cardiovascular Science, Edinburgh University, UK. nick.mills@ed.ac.uk
authors.forename: Nicholas L
authors.initials: NL
authors.lastname: Mills
authors.forename: Kuan Ken
authors.initials: KK
authors.lastname: Lee
authors.forename: David A
authors.initials: DA
authors.lastname: McAllister
authors.forename: Antonia M D
authors.initials: AM
authors.lastname: Churchhouse
authors.forename: Margaret
authors.initials: M
authors.lastname: MacLeod
authors.forename: Mary
authors.initials: M
authors.lastname: Stoddart
authors.forename: Simon
authors.initials: S
authors.lastname: Walker
authors.forename: Martin A
authors.initials: MA
authors.lastname: Denvir
authors.forename: Keith A A
authors.initials: KA
authors.lastname: Fox
authors.forename: David E
authors.initials: DE
authors.lastname: Newby
mesh_terms: D054058:Acute Coronary Syndrome / Q000097:blood* / Q000175:diagnosis; D000368:Aged; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000097:blood / Q000175:diagnosis* / Q000401:mortality; D017063:Outcome Assessment, Health Care; D011379:Prognosis; D011933:Reagent Kits, Diagnostic / Q000592:standards; D012008:Recurrence; D012016:Reference Values; D018570:Risk Assessment; D012606:Scotland; D012680:Sensitivity and Specificity; D014336:Troponin / Q000097:blood* / Q000592:standards
chemical_list: D011933:Reagent Kits, Diagnostic; D014336:Troponin