Assessing random error in the international normalized ratio.
Changes in the international normalized ratio (INR) following warfarin administration may be explained not only by the attendant anticoagulant effect but also, in part, by random errors normally associated with laboratory assays. Thus, a patient's true INR will differ from the reported value by some random error related to the variability in the prothrombin time (PT) assay. By employing a statistical technique known as the delta method, the error expected in an INR for a particular institution can be estimated by taking the product of the international sensitivity index (ISI) and the coefficient of variation (CV) for the PT assay.
Department of Pharmaceutical Services, University of California, Davis Medical Center, Sacramento 95817.
J F
JF
Inciardi
D016903:Drug Monitoring / Q000379:methods*; D006801:Humans; D011517:Prothrombin Time; D014859:Warfarin / Q000627:therapeutic use*
D014859:Warfarin