title: International normalized ratio monitoring of vitamin K antagonist therapy: comparative performance of point-of-care and laboratory-derived testing.
abstract: The monitoring of warfarin therapy using the international normalized ratio (INR) has now moved outside the laboratory's control by use of point-of-care (POC) devices. Although this provides patients with the convenience of immediate results and clinical assessment, POC-INRs are often performed by nonlaboratory staff with little experience in quality control. The Royal College of Pathologists of Australasia Quality Assurance Program (RCPAQAP) Haematology has devised a POC-INR external quality assessment (EQA) program that is suitable for both laboratory and nonlaboratory operators (e.g., nurses) to perform INR testing with good accuracy and precision. A comparison of the performance of the POC versus the laboratory-derived INR testing over the past 8 years has shown that the variation in test results (expressed as coefficient of variation; CV) for laboratory INRs increases with more prolonged INR values, whereas CVs for the POC-INR testing were generally lower, with a reduced dependency on INR values. In our program, the CoaguChek XS (Roche, Basel, Switzerland) showed the best performance among the POC devices. A comparative assessment with other EQA providers showed agreement and disparity with our data in terms of comparative CVs obtained between the laboratory and POC-INRs. The growth of the RCPAQAP POC-INR program from 29 to 360 in the past 12 years highlights the importance of providing suitable EQA for POC-INR staff who are unfamiliar with laboratory practice. This helps maintaining consistent results, which have important implications for the therapeutic management of patients on vitamin K antagonist therapy.
authors.affiliation: Royal College of Pathologists of Australasia Quality Assurance Program (RCPAQAP) Haematology, St. Leonards, New South Wales, Australia.
authors.forename: Roslyn
authors.initials: R
authors.lastname: Bonar
authors.affiliation: Department of Haematology, Institute of Clinical Pathology and Medical Research (ICPMR), Pathology West, NSW Health Pathology, Westmead Hospital, New South Wales, Australia.
authors.forename: Soma
authors.initials: S
authors.lastname: Mohammed
authors.affiliation: Department of Haematology, Institute of Clinical Pathology and Medical Research (ICPMR), Pathology West, NSW Health Pathology, Westmead Hospital, New South Wales, Australia.
authors.forename: Emmanuel J
authors.initials: EJ
authors.lastname: Favaloro
mesh_terms: D000925:Anticoagulants / Q000627:therapeutic use; D001315:Australia; D001777:Blood Coagulation / Q000187:drug effects; D019411:Clinical Laboratory Techniques; D016903:Drug Monitoring / Q000379:methods*; D006487:Hemostasis; D006801:Humans; D007391:International Cooperation; D019934:International Normalized Ratio / Q000592:standards*; D009520:New Zealand; D019095:Point-of-Care Systems; D000067716:Point-of-Care Testing; D011785:Quality Assurance, Health Care; D011786:Quality Control; D015203:Reproducibility of Results; D014812:Vitamin K / Q000037:antagonists & inhibitors*; D014859:Warfarin / Q000008:administration & dosage / Q000097:blood
chemical_list: D000925:Anticoagulants; D014812:Vitamin K; D014859:Warfarin