title: Evaluation of standardization capability of current cardiac troponin I assays by a correlation study: results of an IFCC pilot project.
abstract: BACKGROUND
  As a part of an International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) project to prepare a commutable reference material for cardiac troponin I (cTnI), a pilot study evaluated current cTnI assays for measurement equivalence and their standardization capability.
  
  
  METHODS
  cTnI-positive samples collected from 90 patients with suspected acute myocardial infarction were assessed for method comparison by 16 cTnI commercial assays according to predefined testing protocols. Seven serum pools prepared from these samples were also assessed.
  
  
  RESULTS
  Each assay was assessed against median cTnI concentrations measured by 16 cTnI assays using Passing-Bablok regression analysis of 79 patient samples with values above each assay's declared detection limit. We observed a 10-fold difference in cTnI concentrations for lowest to highest measurement results. After mathematical recalibration of assays, the between-assay variation for patient samples reduced on average from 40% to 22% at low cTnI concentration, 37%-20% at medium concentration, and 29%-14% at high concentration. The average reduction for pools was larger at 16%, 13% and 7% for low, medium and high cTnI concentrations, respectively. Overall, assays demonstrated negligible bias after recalibration (y-intercept: -1.4 to 0.3 ng/L); however, a few samples showed substantial positive and/or negative differences for individual cTnI assays.
  
  
  CONCLUSIONS
  All of the 16 commercial cTnI assays evaluated in the study demonstrated a significantly higher degree of measurement equivalence after mathematical recalibration, indicating that measurement harmonization or standardization would be effective at reducing inter-assay bias. Pooled sera behaved similarly to individual samples in most assays.
authors.forename: Jillian R
authors.initials: JR
authors.lastname: Tate
authors.forename: David M
authors.initials: DM
authors.lastname: Bunk
authors.forename: Robert H
authors.initials: RH
authors.lastname: Christenson
authors.forename: Julian H
authors.initials: JH
authors.lastname: Barth
authors.forename: Alexey
authors.initials: A
authors.lastname: Katrukha
authors.forename: James E
authors.initials: JE
authors.lastname: Noble
authors.forename: Heinz
authors.initials: H
authors.lastname: Schimmel
authors.forename: Lili
authors.initials: L
authors.lastname: Wang
authors.forename: Mauro
authors.initials: M
authors.lastname: Panteghini
mesh_terms: D000293:Adolescent; D001774:Blood Chemical Analysis / Q000592:standards*; D002138:Calibration; D005260:Female; D006801:Humans; D009206:Myocardium / Q000378:metabolism; D010865:Pilot Projects; D012015:Reference Standards; D019210:Troponin I / Q000097:blood*; D055815:Young Adult
chemical_list: D019210:Troponin I