title: Assessment of the validity of the INR system for patients with liver impairment.
abstract: The INR system was developed to standardize PT reporting in patients on oral anticoagulants. We prospectively collected blood samples from 29 patients with liver impairment (INR 1.5-3.5). Control patients were on warfarin (n = 31). PT's were measured on an ACL-300 with three thromboplastin reagents. INR's were calculated using instrument specific ISI's. Other tests performed were FDP's, fibrinogen, aPTT, factors II, V, VII and X. The INR's for each patient in the study population using the three thromboplastin reagents were significantly different (p = 0.0001). Those for the control population were not (p = 0.0658). Fibrinogen, factors V, II and X were different at the 5% level of significance between the populations. FDP's were detected in 17 study subjects. The INR system is not valid for comparison of patients with liver impairment because different reagents do not give the same INR for the same sample. It is, however, no less valid than the use of PT with different thromboplastin reagents. Further study is recommended.
authors.affiliation: Department of Hematology/Blood Bank, Victoria Hospital, London, Ontario, Canada.
authors.forename: M J
authors.initials: MJ
authors.lastname: Kovacs
authors.forename: A
authors.initials: A
authors.lastname: Wong
authors.forename: K
authors.initials: K
authors.lastname: MacKinnon
authors.forename: K
authors.initials: K
authors.lastname: Weir
authors.forename: M
authors.initials: M
authors.lastname: Keeney
authors.forename: E
authors.initials: E
authors.lastname: Boyle
authors.forename: M
authors.initials: M
authors.lastname: Cruickshank
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D007202:Indicators and Reagents; D008107:Liver Diseases / Q000097:blood*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011517:Prothrombin Time; D012015:Reference Standards; D015203:Reproducibility of Results; D013925:Thromboplastin; D014859:Warfarin / Q000627:therapeutic use; D014944:World Health Organization
chemical_list: D007202:Indicators and Reagents; D014859:Warfarin; D013925:Thromboplastin