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Measurement of low molecular weight heparin ex vivo activities in clinical laboratories using various anti-Xa assays: interlaboratory variability and requirement for an agreed low molecular weight heparin standard. 1987

P Sié, and M F Aillaud, and D de Prost, and C Droullé, and F Forestier, and P Guedj, and I Juhan-Vague, and B Polack, and G Potron, and M Roncato
Haemostasis laboratories, Hôpital Purpan, Toulouse, France.

The only sensitive and convenient assay to assess the biological activity of low molecular weight heparins (LMWHs) is based on the potentiation of activated factor Xa inhibition. Several procedures for measuring the socalled anti Xa activity have been proposed. In this collaborative study including eight laboratories, we have used four different assays (three amidolytic and one clotting based methods) for measuring the anti Xa activity of ex vivo samples obtained after injecting three different LMWHs. The dispersion of the results obtained by calibration against standard heparin could be reduced by using any of the three LMWHs for calibration. A coefficient of variation less than 0.20 between values obtained in different laboratories using a variety of methods seems acceptable. However it is necessary to refer to a common international standard for expressing the results in units and to define, for each of the three products, the therapeutic range.

UI MeSH Term Description Entries
D012015 Reference Standards A basis of value established for the measure of quantity, weight, extent or quality, e.g. weight standards, standard solutions, methods, techniques, and procedures used in diagnosis and therapy. Standard Preparations,Standards, Reference,Preparations, Standard,Standardization,Standards,Preparation, Standard,Reference Standard,Standard Preparation,Standard, Reference
D006495 Heparin, Low-Molecular-Weight Heparin fractions with a molecular weight usually between 4000 and 6000 kD. These low-molecular-weight fractions are effective antithrombotic agents. Their administration reduces the risk of hemorrhage, they have a longer half-life, and their platelet interactions are reduced in comparison to unfractionated heparin. They also provide an effective prophylaxis against postoperative major pulmonary embolism. LMWH,Low-Molecular-Weight Heparin,Low Molecular Weight Heparin,Heparin, Low Molecular Weight
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D015842 Serine Proteinase Inhibitors Exogenous or endogenous compounds which inhibit SERINE ENDOPEPTIDASES. Serine Endopeptidase Inhibitor,Serine Endopeptidase Inhibitors,Serine Protease Inhibitor,Serine Protease Inhibitors,Serine Proteinase Antagonist,Serine Proteinase Antagonists,Serine Proteinase Inhibitor,Serine Proteinase Inhibitors, Endogenous,Serine Proteinase Inhibitors, Exogenous,Serine Protease Inhibitors, Endogenous,Serine Protease Inhibitors, Exogenous,Antagonist, Serine Proteinase,Endopeptidase Inhibitor, Serine,Inhibitor, Serine Endopeptidase,Inhibitor, Serine Protease,Inhibitor, Serine Proteinase,Protease Inhibitor, Serine,Proteinase Antagonist, Serine,Proteinase Inhibitor, Serine
D015951 Factor Xa Activated form of factor X that participates in both the intrinsic and extrinsic pathways of blood coagulation. It catalyzes the conversion of prothrombin to thrombin in conjunction with other cofactors. Autoprothrombin C,Coagulation Factor Xa,Factor X, Activated,Thrombokinase,Activated Factor X,Blood Coagulation Factor X, Activated,Factor 10A,Factor Ten A,Factor Xa, Coagulation

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