Use of INR calibrator plasmas in the routine coagulation laboratory: a study of two thrombolastin reagents.

INR values may be either calculated with the ISI values supplied by thromboplastin manufacturers or are directly extrapolated from certified INR calibrator plasmas. We tested the principle of local INR calibration using INR calibrator plasmas (PT-Multi Calibrator, Siemens), two thromboplastin reagents (Neoplastin Plus, rabbit brain, Stago, coagulometer-specific ISI 1.31, and Innovin, recombinant human tissue factor, Siemens) and the same coagulometer (STA-R, Stago) in 100 patients on warfarin.

Relationship between international normalized ratio values, vitamin K-dependent clotting factor levels and in vivo prothrombin activation during the early and steady phases of oral anticoagulant treatment.

Background And Objectives: In vitro studies have shown that the rate of prothrombin activation is linearly related to the concentration of factor II (FII) in the assay system, suggesting a key role of prothrombin levels in the expression of the antithrombotic activity of oral anticoagulant treatment (OAT). We investigated the in vivo relationship between prothrombin activation and vitamin K-dependent clotting factor levels during the early and steady phases of OAT in patients and in healthy volunteers.

Design And Methods: The changes in international normalizezd ratio (INR) and in the plasma levels of FVII, FX, FII, protein C (PC) and prothrombin fragment 1.

Interference of lupus anticoagulants in prothrombin time assays: implications for selection of adequate methods to optimize the management of thrombosis in the antiphospholipid-antibody syndrome.

Background And Objective: Prolonged anticoagulation aiming at International Normalized Ratio (INR) values > 3.0 has been recommended for patients with thrombosis and the antiphospholipid-antibody syndrome. We evaluated the influence of anticoagulant antibodies in two different prothrombin time (PT) assays carried out on plasma from lupus anticoagulant patients on oral anticoagulation.

Potential failure of the International Normalized Ratio (INR) System in the monitoring of oral anticoagulation in patients with lupus anticoagulants.

Patients with antiphospholipid antibody syndrome (APS) experience a higher rate of recurrence of thrombosis than the general population of patients with thrombotic disease. Based on a retrospective analysis, it has been suggested that patients with APS should be kept on prolonged anticoagulation aiming at international normalised ratio (INR) values > 3.0.