title: Analytical performance of the i-STAT cardiac troponin I assay.
abstract: BACKGROUND
  This study determines the analytical characteristics of the i-STAT cardiac troponin I assay (cTnI; i-STAT, Princeton, NJ), a 10-min POC assay, designed to be performed at the bedside.
  
  
  METHODS
  Three different hospitals participated in a patient specimen and analytical validation study (n=186) for the i-STAT cTnI assay carried out in real time. A total of 186 whole blood specimens (lithium heparin) were collected from patients presenting with symptoms suggestive of acute coronary syndromes (ACS) for correlation studies as well as from 162 healthy subjects for reference interval determination. Factors studied included antibody specificity, detection limit, imprecision, linearity, assay specificity, sample type stability, interferences, reference limit determination and comparison vs. the Dade Stratus CS cTnI assay.
  
  
  RESULTS
  Total imprecision (CV) of 10% and 20% were seen at 0.09 and 0.07 microg/l, respectively. The detection limit was 0.02 microg/l. The 99th percentile reference limit was 0.08 microg/l. The assay was not affected by common interferents. An equimolar response within 5% was found for reduced and phosphorylated forms of TIC and IC complexes. Regression analysis for the i-STAT cTnI between whole blood and plasma specimens and for whole blood between the i-STAT and Stratus CS cTnI assays demonstrated slopes of 1.06 and 0.89, respectively.
  
  
  CONCLUSIONS
  The i-STAT cTnI assay is a sensitive and precise monitor of cTnI, poised for point-of-care/near bedside clinical utilization for triage, diagnostics and risk management of acute coronary syndrome patients.
authors.affiliation: Department of Laboratory Medicine and Pathology, Hennepin County Medical Center and University of Minnesota School of Medicine, Clinical Labs P4, 701 Park Avenue, Minneapolis, MN 55415, USA. fred.apple@co.hennepin.mn.us
authors.forename: Fred S
authors.initials: FS
authors.lastname: Apple
authors.forename: MaryAnn M
authors.initials: MM
authors.lastname: Murakami
authors.forename: Robert H
authors.initials: RH
authors.lastname: Christenson
authors.forename: John L
authors.initials: JL
authors.lastname: Campbell
authors.forename: Cary J
authors.initials: CJ
authors.lastname: Miller
authors.forename: Karl G
authors.initials: KG
authors.lastname: Hock
authors.forename: Mitchell G
authors.initials: MG
authors.lastname: Scott
mesh_terms: D000328:Adult; D000368:Aged; D000911:Antibodies, Monoclonal; D002138:Calibration; D003327:Coronary Disease / Q000175:diagnosis* / Q000378:metabolism; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009206:Myocardium / Q000737:chemistry*; D019095:Point-of-Care Systems; D019210:Troponin I / Q000737:chemistry*
chemical_list: D000911:Antibodies, Monoclonal; D019210:Troponin I