title: Evaluation of High-Sensitivity Cardiac Troponin I Levels in Patients With Suspected Acute Coronary Syndrome.
abstract: Low concentrations of high-sensitivity cardiac troponin I determined on presentation to the emergency department (ED) have been shown to have an excellent negative predictive value (NPV) for the identification of acute myocardial infarction. The sensitivity, and therefore clinical applicability, of such testing strategies is unknown.
  
  
  
  To determine the diagnostic performance of low concentrations of high-sensitivity cardiac troponin I in patients with suspected cardiac chest pain and an electrocardiogram showing no ischemia as an indicator of acute myocardial infarction.
  
  
  
  A pooled analysis of 5 international (Australia, New Zealand, and England) prospective, observational cohort studies with blinded outcome assessment and 30-day follow-up was conducted. A total of 3155 patients presenting with symptoms suggestive of cardiac ischemia were included in the analysis. Eligible patients had a nonischemic electrocardiogram determined and high-sensitivity troponin I measured at presentation. The lower limit of detection (1.2 ng/L) as well as cutoff concentrations rounded to the nearest integer for a high-sensitivity troponin I assay were used in the analysis. Recruitment was undertaken from November 1, 2007, to August 10, 2013.
  
  
  
  The primary outcome was fatal or nonfatal acute myocardial infarction occurring within 30 days of ED presentation, adjudicated with serial troponin testing. The secondary outcome was the proportion of patients potentially suitable for early discharge at each cutoff concentration.
  
  
  
  Of the 3155 eligible patients, 1771 were male (56.1%), and mean (SD) age was 57.4 (13.3) years. Acute myocardial infarction developed in 291 individuals (9.2%). The 1.2-ng/L limit of detection gave a sensitivity of 99.0% (95% CI, 96.8%-99.7%) and an NPV of 99.5% (95% CI, 98.4%-99.9%). This cutoff level would allow for early discharge of 594 patients (18.8%). All higher rounded cutoff values had sensitivities less than 98.0%. Diagnostic performance of the limit of detection was maintained when patients were stratified by age, sex, risk factors, presence of coronary artery disease, and early presentation.
  
  
  
  High-sensitivity troponin I concentrations determined at presentation to the ED that were below the limit of detection identified 18.8% of patients potentially suitable for discharge, with a high sensitivity for acute myocardial infarction. Rounded cutoff values above the limit of detection may not have the required sensitivity for clinical implementation.
authors.affiliation: Emergency Department, Southmead Hospital, North Bristol National Health Service Trust, Bristol, England.
authors.forename: Edward
authors.initials: E
authors.lastname: Carlton
authors.affiliation: Emergency Medicine, Royal Brisbane and Women's Hospital, Brisbane, Australia3School of Medicine, The University of Queensland, Brisbane, Australia4School of Public Health, Queensland University of Technology, Brisbane, Australia.
authors.forename: Jaimi
authors.initials: J
authors.lastname: Greenslade
authors.affiliation: Emergency Medicine, Royal Brisbane and Women's Hospital, Brisbane, Australia3School of Medicine, The University of Queensland, Brisbane, Australia4School of Public Health, Queensland University of Technology, Brisbane, Australia.
authors.forename: Louise
authors.initials: L
authors.lastname: Cullen
authors.affiliation: Central Manchester University Hospitals, National Health Service Foundation Trust, Manchester, England.
authors.forename: Richard
authors.initials: R
authors.lastname: Body
authors.affiliation: Department of Emergency Medicine, Christchurch Hospital, Christchurch, New Zealand.
authors.forename: Martin
authors.initials: M
authors.lastname: Than
authors.affiliation: Department of Emergency Medicine, Christchurch Hospital, Christchurch, New Zealand7Department of Medicine, University of Otago, Christchurch, New Zealand.
authors.forename: John W
authors.initials: JW
authors.lastname: Pickering
authors.affiliation: Department of Emergency Medicine, Christchurch Hospital, Christchurch, New Zealand.
authors.forename: Sally
authors.initials: S
authors.lastname: Aldous
authors.affiliation: Central Manchester University Hospitals, National Health Service Foundation Trust, Manchester, England.
authors.forename: Simon
authors.initials: S
authors.lastname: Carley
authors.affiliation: Emergency Medicine, Royal Brisbane and Women's Hospital, Brisbane, Australia.
authors.forename: Christopher
authors.initials: C
authors.lastname: Hammett
authors.affiliation: Emergency Department, Southmead Hospital, North Bristol National Health Service Trust, Bristol, England.
authors.forename: Jason
authors.initials: J
authors.lastname: Kendall
authors.affiliation: Central Manchester University Hospitals, National Health Service Foundation Trust, Manchester, England.
authors.forename: Brian
authors.initials: B
authors.lastname: Keevil
authors.affiliation: School of Medicine, The University of Notre Dame, Sydney, Australia.
authors.forename: Sarah
authors.initials: S
authors.lastname: Lord
authors.affiliation: Emergency Medicine, Royal Brisbane and Women's Hospital, Brisbane, Australia.
authors.forename: William
authors.initials: W
authors.lastname: Parsonage
authors.affiliation: Sunshine Coast Hospital and Health Services, University of the Sunshine Coast, Nambour, Australia.
authors.forename: Kim
authors.initials: K
authors.lastname: Greaves
mesh_terms: D054058:Acute Coronary Syndrome / Q000150:complications / Q000175:diagnosis*; D000328:Adult; D000368:Aged; D001315:Australia; D002637:Chest Pain / Q000209:etiology; D015331:Cohort Studies; D004739:England; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000175:diagnosis; D009520:New Zealand; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D019210:Troponin I / Q000097:blood*
chemical_list: D019210:Troponin I