Factor X and factor II activity levels do not always agree in warfarin-treated lupus anticoagulant patients. 2010

Terry K Rosborough, and Jennifer M Jacobsen, and Michele F Shepherd
Medical Education Department and Coagulation Laboratory, Abbott Northwestern Hospital, Minneapolis, Minnesota 55407, USA.

Warfarin therapy is used in lupus anticoagulant patients with thrombosis and yet the prothrombin time (PT)/international normalized ratio (INR) in these patients can sometimes be falsely elevated. Both a PT-based factor II (FII) assay and a chromogenic, enzymatic factor X (CFX) assay have been used for monitoring when the INR may be artifactual. This study compared FII and CFX assays in lupus anticoagulant-positive and lupus anticoagulant-negative warfarin-treated patients in a cross-sectional study of samples from 21 lupus anticoagulant-positive and 19 lupus anticoagulant-negative outpatients. Plasma samples were simultaneously measured for FII and CFX and the ratio of FII/CFX was used to measure concordance. Compared with lupus anticoagulant-negative patients 14 of the 21 lupus anticoagulant-positive patients had lower FII/CFX ratios (P < 0.01). Three of the patients had ratios less than 0.6 indicating strong disagreement (P < 0.0001). The patient with the lowest FII/CFX ratio had evidence suggesting a specific antibody to FII. Another patient showed that the discordance between FII and CFX varied over time. The CFX assay in the laboratory was technically superior, more precise, and less costly. The CFX assay is preferred for warfarin therapy monitoring in lupus anticoagulant patients when INR artifacts are suspected.

UI MeSH Term Description Entries
D011516 Prothrombin A plasma protein that is the inactive precursor of thrombin. It is converted to thrombin by a prothrombin activator complex consisting of factor Xa, factor V, phospholipid, and calcium ions. Deficiency of prothrombin leads to hypoprothrombinemia. Coagulation Factor II,Factor II,Blood Coagulation Factor II,Differentiation Reversal Factor,Factor II, Coagulation,Factor, Differentiation Reversal,II, Coagulation Factor
D003430 Cross-Sectional Studies Studies in which the presence or absence of disease or other health-related variables are determined in each member of the study population or in a representative sample at one particular time. This contrasts with LONGITUDINAL STUDIES which are followed over a period of time. Disease Frequency Surveys,Prevalence Studies,Analysis, Cross-Sectional,Cross Sectional Analysis,Cross-Sectional Survey,Surveys, Disease Frequency,Analyses, Cross Sectional,Analyses, Cross-Sectional,Analysis, Cross Sectional,Cross Sectional Analyses,Cross Sectional Studies,Cross Sectional Survey,Cross-Sectional Analyses,Cross-Sectional Analysis,Cross-Sectional Study,Cross-Sectional Surveys,Disease Frequency Survey,Prevalence Study,Studies, Cross-Sectional,Studies, Prevalence,Study, Cross-Sectional,Study, Prevalence,Survey, Cross-Sectional,Survey, Disease Frequency,Surveys, Cross-Sectional
D005170 Factor X Storage-stable glycoprotein blood coagulation factor that can be activated to factor Xa by both the intrinsic and extrinsic pathways. A deficiency of factor X, sometimes called Stuart-Prower factor deficiency, may lead to a systemic coagulation disorder. Autoprothrombin III,Coagulation Factor X,Stuart Factor,Stuart-Prower Factor,Blood Coagulation Factor X,Factor 10,Factor Ten,Stuart Prower Factor,Factor X, Coagulation
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000925 Anticoagulants Agents that prevent BLOOD CLOTTING. Anticoagulant Agent,Anticoagulant Drug,Anticoagulant,Anticoagulant Agents,Anticoagulant Drugs,Anticoagulation Agents,Indirect Thrombin Inhibitors,Agent, Anticoagulant,Agents, Anticoagulant,Agents, Anticoagulation,Drug, Anticoagulant,Drugs, Anticoagulant,Inhibitors, Indirect Thrombin,Thrombin Inhibitors, Indirect
D013927 Thrombosis Formation and development of a thrombus or blood clot in BLOOD VESSELS. Atherothrombosis,Thrombus,Blood Clot,Blood Clots,Thromboses
D014859 Warfarin An anticoagulant that acts by inhibiting the synthesis of vitamin K-dependent coagulation factors. Warfarin is indicated for the prophylaxis and/or treatment of venous thrombosis and its extension, pulmonary embolism, and atrial fibrillation with embolization. It is also used as an adjunct in the prophylaxis of systemic embolism after myocardial infarction. Warfarin is also used as a rodenticide. 4-Hydroxy-3-(3-oxo-1-phenylbutyl)-2H-1-benzopyran-2-one,Aldocumar,Apo-Warfarin,Coumadin,Coumadine,Gen-Warfarin,Marevan,Tedicumar,Warfant,Warfarin Potassium,Warfarin Sodium,Potassium, Warfarin,Sodium, Warfarin
D016682 Lupus Coagulation Inhibitor An antiphospholipid antibody found in association with a variety of diseases (e.g., SYSTEMIC LUPUS ERYTHEMATOSUS and ANTIPHOSPHOLIPID SYNDROME) as well as in healthy individuals. In vitro, the antibody interferes with the conversion of prothrombin to thrombin and prolongs the partial thromboplastin time. In vivo, it exerts a procoagulant effect resulting in thrombosis mainly in the larger veins and arteries. It further causes obstetrical complications, including fetal death and spontaneous abortion, as well as a variety of hematologic and neurologic complications. Lupus Anticoagulant,Lupus Anticoagulant Autoantibodies,Lupus Anticoagulant Autoantibody,Anticoagulant, Lupus,Coagulation Inhibitor, Lupus,Inhibitor, Lupus Coagulation,Anticoagulant Autoantibody, Lupus,Autoantibody, Lupus Anticoagulant

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