title: Clinical impact of point-of-care vs laboratory measurement of anticoagulation.
abstract: Patients using anticoagulation point-of-care (POC) monitors are advised to periodically test these systems against laboratory methods to monitor performance. The international normalized ratio (INR), however, can vary between test systems owing to different instrument-reagent combinations. In a randomized study evaluating warfarin self-management, we compared INR measured by patients on a POC monitor (ProTime, International Technidyne Corporation, Edison, NJ) with those obtained at a hospital laboratory within 1 hour Ninety-one paired INR determinations from 55 patients met inclusion criteria. Clinical agreement in which POC and laboratory INR were within or outside the target INR range occurred in 56 (62%) of 91 cases (kappa = 0.35). The mean (SD) difference between POC and laboratory INR was 0.44 (0.61). Six pairs differed by 1 or more INR units, 3 at study initiation resulting in POC monitor replacement. The accuracy of INR self-testing with ProTime was acceptable. The small failure rate of INR agreement might be clinically important, suggesting the need for external quality control systems.
authors.affiliation: Cardiology, Pharmaceutical Sciences Clinical Service Unit, Vancouver General Hospital, BC, Canada.
authors.forename: Rubina
authors.initials: R
authors.lastname: Sunderji
authors.forename: Kenneth
authors.initials: K
authors.lastname: Gin
authors.forename: Karen
authors.initials: K
authors.lastname: Shalansky
authors.forename: Cedric
authors.initials: C
authors.lastname: Carter
authors.forename: Keith
authors.initials: K
authors.lastname: Chambers
authors.forename: Cheryl
authors.initials: C
authors.lastname: Davies
authors.forename: Linda
authors.initials: L
authors.lastname: Schwartz
authors.forename: Anthony
authors.initials: A
authors.lastname: Fung
mesh_terms: D000328:Adult; D000368:Aged; D000925:Anticoagulants / Q000097:blood*; D005260:Female; D006801:Humans; D019934:International Normalized Ratio / Q000379:methods*; D008297:Male; D008875:Middle Aged; D019095:Point-of-Care Systems; D011786:Quality Control; D015203:Reproducibility of Results; D014859:Warfarin / Q000097:blood*
chemical_list: D000925:Anticoagulants; D014859:Warfarin