title: High-sensitivity cardiac troponin t concentrations below the limit of detection to exclude acute myocardial infarction: a prospective evaluation.
abstract: BACKGROUND
  Initial reports suggest that concentrations of high-sensitivity cardiac troponin T (hs-cTnT) (Roche Diagnostics Elecsys(®)) below the limit of blank (LoB) (3 ng/L) or limit of detection (LoD) (5 ng/L) of the assay have almost 100% negative predictive value (NPV) for acute myocardial infarction (AMI), particularly among patients without electrocardiograph (ECG) evidence of ischemia. We aimed to prospectively validate those findings.
  
  
  METHODS
  We included adults presenting to the emergency department with suspected cardiac chest pain. Standard troponin T (cTnT) and hs-cTnT (both Roche Elecsys) were tested in samples drawn on arrival. The primary outcome was AMI, adjudicated by 2 investigators on the basis of clinical data and ≥12-h cTnT testing. We also evaluated diagnostic performance when AMI was readjudicated on the basis of hs-cTnT (≥12-h) concentrations.
  
  
  RESULTS
  Of 463 patients included, 79 (17.1%) had AMI. Twenty-four patients (5.2%) had hs-cTnT concentrations below the LoB, although none had AMI. Ninety-six patients (20.7%) had hs-cTnT concentrations below the LoD, 1 of whom had AMI. Thus, diagnostic sensitivity was 98.7% (95% CI 87.5%-98.6%) and NPV was 99.0% (95% CI 94.3%-100.0%). Of the 17.3% (n = 80) patients with hs-cTnT below the LoD and no ECG ischemia, none had AMI. Thus, diagnostic sensitivity was 100.0% (95% CI 95.4%-100.0%) and NPV was 100.0% (95% CI 95.5%-100.0%). Sensitivity and NPV were maintained when AMI was readjudicated on the basis of hs-cTnT.
  
  
  CONCLUSIONS
  Our findings confirm that patients with nonischemic ECG and undetectable hs-cTnT at presentation have a very low probability of AMI, although the proportion of patients affected was smaller than in previous research.
authors.affiliation: The University of Manchester, Oxford Road, Manchester, UK; Central Manchester University Hospitals Foundation NHS Trust, Manchester Academic Health Science Centre, Oxford Road, Manchester, UK; richard.body@manchester.ac.uk.
authors.forename: Richard
authors.initials: R
authors.lastname: Body
authors.affiliation: Stockport NHS Foundation Trust, Poplar Grove, Stockport, UK;
authors.forename: Gillian
authors.initials: G
authors.lastname: Burrows
authors.affiliation: Central Manchester University Hospitals Foundation NHS Trust, Manchester Academic Health Science Centre, Oxford Road, Manchester, UK; Manchester Metropolitan University, Hathersage Road, Manchester, UK;
authors.forename: Simon
authors.initials: S
authors.lastname: Carley
authors.affiliation: Royal Brisbane and Women's Hospital, Brisbane, Australia;
authors.forename: Louise
authors.initials: L
authors.lastname: Cullen
authors.affiliation: University of Otago, Christchurch, New Zealand;
authors.forename: Martin
authors.initials: M
authors.lastname: Than
authors.affiliation: Mayo Clinic and Mayo College of Medicine, Rochester, MN.
authors.forename: Allan S
authors.initials: AS
authors.lastname: Jaffe
authors.affiliation: Stockport NHS Foundation Trust, Poplar Grove, Stockport, UK;
authors.forename: Philip S
authors.initials: PS
authors.lastname: Lewis
mesh_terms: D000208:Acute Disease; D000368:Aged; D015415:Biomarkers / Q000097:blood*; D002637:Chest Pain / Q000175:diagnosis; D004562:Electrocardiography; D005260:Female; D006801:Humans; D007902:Length of Stay; D057230:Limit of Detection; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000097:blood / Q000175:diagnosis*; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012372:ROC Curve; D012680:Sensitivity and Specificity; D020107:Troponin T / Q000097:blood*
chemical_list: D015415:Biomarkers; D020107:Troponin T