title: Accuracy of point of care coagulometers compared to reference laboratory measurements in patients on oral anticoagulation therapy.
abstract: BACKGROUND
  Vitamin K antagonists (VKA) are widely prescribed throughout the world. Patients on VKA therapy require international normalized ratio (INR) monitoring of venous blood to ensure the response remains within the therapeutic window. Point-of-care devices (POC-INR) can safely and easily monitor VKA efficacy but need to be evaluated in practice. The aim of this study was to assess the precision and accuracy of a new POC-INR (Qlab) compared to the laboratory plasma technique and the CoaguChek-XS system.
  
  
  METHODS
  Consecutive patients on VKA referred to our institution were included. The study was designed to analyze 75 patients divided equally in the following subgroups: INR<2; INR=2-3; INR>3. INR was measured with an established laboratory method (INRREF) with an international sensitivity index of 1.0 and by two different POC-INRs: the Qlab (INRQlab) and the CoaguChek-XS systems (INRXS).
  
  
  RESULTS
  82 patients treated mainly for atrial fibrillation or venous thromboembolism disease were included. Precision in therapeutic range (INR=2-3) of both POC-INRs was satisfactory with a coefficient of variation of 4.6% for the Qlab and 4.3% for the CoaguChek-XS. INRRef was 2.70 ± 1.36, INRQlab 2.59 ± 1.25 and INRXS 2.89 ± 1.37. Accuracy was low with the Qlab (R(2)=0.64) and higher with the CoaguChek-XS (R(2)=0.94). The mean relative difference from the INRRef was higher for the Qlab (18.4%) than for the CoaguChek-XS (12.9%). Clinical concordance was lower with the Qlab (78.2%) than with the CoaguChek-XS (90.0%).
  
  
  CONCLUSIONS
  This study suggests that the Qlab has accuracy limitations with clinical consequences. New POC-INR devices require careful evaluation prior to clinical implementation.
authors.affiliation: Department of Cardiology, Inserm U942, Lariboisiere Hospital, AP-HP, Paris Diderot University, Sorbonne Paris Cité, Paris, France; Thrombosis and Atherosclerosis Research Unit, Vessels and Blood Institute (IVS), Anticoagulation Clinic (CREATIF), Lariboisiere Hospital, Paris VII University, EA 7334 REMES, Paris, France. Electronic address: jean-guillaume.dillinger@aphp.fr.
authors.forename: Jean-Guillaume
authors.initials: JG
authors.lastname: Dillinger
authors.affiliation: Department of Cardiology, Inserm U942, Lariboisiere Hospital, AP-HP, Paris Diderot University, Sorbonne Paris Cité, Paris, France.
authors.forename: Thiziri
authors.initials: T
authors.lastname: Si Moussi
authors.affiliation: Thrombosis and Atherosclerosis Research Unit, Vessels and Blood Institute (IVS), Anticoagulation Clinic (CREATIF), Lariboisiere Hospital, Paris VII University, EA 7334 REMES, Paris, France.
authors.forename: Natacha
authors.initials: N
authors.lastname: Berge
authors.affiliation: Thrombosis and Atherosclerosis Research Unit, Vessels and Blood Institute (IVS), Anticoagulation Clinic (CREATIF), Lariboisiere Hospital, Paris VII University, EA 7334 REMES, Paris, France.
authors.forename: Claire
authors.initials: C
authors.lastname: Bal Dit Sollier
authors.affiliation: Department of Cardiology, Inserm U942, Lariboisiere Hospital, AP-HP, Paris Diderot University, Sorbonne Paris Cité, Paris, France.
authors.forename: Patrick
authors.initials: P
authors.lastname: Henry
authors.affiliation: Thrombosis and Atherosclerosis Research Unit, Vessels and Blood Institute (IVS), Anticoagulation Clinic (CREATIF), Lariboisiere Hospital, Paris VII University, EA 7334 REMES, Paris, France.
authors.forename: Ludovic
authors.initials: L
authors.lastname: Drouet
mesh_terms: D000284:Administration, Oral; D000328:Adult; D000368:Aged; D000925:Anticoagulants / Q000008:administration & dosage / Q000627:therapeutic use*; D001281:Atrial Fibrillation / Q000188:drug therapy*; D001777:Blood Coagulation / Q000187:drug effects; D016903:Drug Monitoring; D005260:Female; D006801:Humans; D019934:International Normalized Ratio; D008297:Male; D008875:Middle Aged; D019095:Point-of-Care Systems; D011517:Prothrombin Time; D054556:Venous Thromboembolism / Q000188:drug therapy*; D014812:Vitamin K / Q000037:antagonists & inhibitors*
chemical_list: D000925:Anticoagulants; D014812:Vitamin K
keywords: International normalized ratio; Oral anticoagulant; Point-of-care testing; Prothrombin time; Vitamin K antagonist