Factor X Deficiency Workup

Updated: Feb 16, 2021
  • Author: Robert A Schwartz, MD, MPH; Chief Editor: Perumal Thiagarajan, MD  more...
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Laboratory Studies

Coagulation study findings in patients with factor X deficiency include the following:

  • The prothrombin time (PT) is prolonged
  • The activated partial thromboplastin time (aPTT) is prolonged
  • The Russell viper venom time (RVVT) is prolonged; Russell viper venom cleaves factor X to produce active factor Xa
  • Bleeding time is within the reference range

Results of factor X assays may vary, depending on whether the deficiency is type I (reduced synthesis of factor X) or type 2 (production of dysfunctional factor X). In patients with a type I deficiency, both functional and antigenic factor X levels are decreased. In patients with a type II X deficiency, the functional level is decreased and the antigenic level varies from within the reference range to a decreased level (production of dysfunctional factor X)

In isolated factor X deficiency, assays of other clotting factors should reveal levels within their respective reference ranges. In factor X deficiency due to vitamin K deficiency or vitamin K antagonist use, assays of other clotting factors reveal decreases in all vitamin K–dependent factors (ie, factor II, factor VII, factor IX, factor X, protein C). Liver disease causes a decrease in the levels of many clotting factors.