Paul B, Oxley A, Brigham K, Cox T, Hamilton PJ. Factor II, VII, IX and X concentrations in patients receiving long term warfarin.
J Clin Pathol 1987;
40:94-8. [PMID:
3818977 PMCID:
PMC1140836 DOI:
10.1136/jcp.40.1.94]
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Abstract
Using standard one stage clotting assays the concentrations of factors II, VII, IX and X were determined in 37 patients stabilised on warfarin for between three months and 17 years. Contrary to popular belief, the concentrations were not equally depressed, with factor X the lowest, factor II at intermediate value, factors VII and IX the highest. Some 71% of the variance of the British corrected ratio (BCR) could be accounted for by measurement of the factors assayed. Analysis of this variance showed 91% of the explained variance attributable to factor II, 7% to factor VII, 1.6% to factor IX and 0.4% to factor X. With the sudden and recent withdrawal of human thromboplastin, investigation of the sensitivities of the animal thromboplastins to changes in vitamin K dependent factors in orally anticoagulated patients is needed to ensure that the potentially alarming falls in factors II and X in these patients are being adequately detected.
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