ALTERED FACTOR-VII ACTIVITY IN HEMOPHILIA

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  • 1 January 1985
    • journal article
    • research article
    • Vol. 65  (4) , 845-849
Abstract
Factor VII levels were studied in hemophilia A and B plasmas and normal controls in a controlled, prospective study. Three assay methods were used: a standard clotting assay (FVIIc-A); a modified clotting assay (FVIIc-B) and a coupled amidolytic assay. By the FVIIc-B assay, the hemophilic plasmas were significantly lower than in the normal group (68.2 .+-. 3.3% [SE] and 83.5 .+-. 3.8%, respectively; P < 0.01). The amidolytic assay which measures total factor VII regardless of its activity state (factor VII or VIIa), was higher in the patient group than in the control group (126.9 .+-. 9.6% and 99.4 .+-. 5.7%, respectively; P < 0.01). Control experiments showed that the differences in FVIIc-B activity were not caused by artifactual activation of factor VII ex vivo in the control group. The mean FVIIc-A assay of hemophilic plasmas (126.3 .+-. 6.5%) agreed closely with the amidolytic assay, suggesting that the FVIIc-A method is also insensitive to the factor VII activity state. The FVIIc-B assay apparently is more sensitive to the presence of factor VIIa. The increased sensitivity of the FVIIc-B assay to factor VII activation was confirmed by comparision of the 2 clotting assays on plama subjected to activation in glass at 4.degree. C. Factor VII in hemophilic plasma apparently is less activated than in normal plasma. Whether this contributes to the bleeding diathesis of hemophilia is unknown. Factor VII in vivo apparently is normally subject to some degree of activation by an enzyme (or enzymes) generated by a turnover of the intrinsic pathway.