What is the role of lab tests in the workup of factor V deficiency?

Updated: Mar 09, 2021
  • Author: Olga Kozyreva, MD; Chief Editor: Perumal Thiagarajan, MD  more...
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The presence of a mild prolongation of the prothrombin time (PT) and activated partial thromboplastin time (aPTT) may be the first indication of factor V deficiency. Coagulation study results are as follows:

  • Bleeding time can be prolonged in severe cases
  • aPTT - Prolonged
  • PT - Prolonged
  • Thrombin time - Normal
  • Stypven time (Russell viper venom time [RVVT]) - Prolonged
  • Mixing study - Correction of PT or partial thromboplastin time (PTT) with the mixing of equal amounts of normal and patient plasma

Use specific factor V activity and antigen assays for confirmation. The factor V antigen assay quantifies factor V levels but does not test for functional factor V. Some patients have factor V deficiency caused by dysfunctional factor V while the level of factor V protein, estimated by factor V antigen levels, is normal. [21] However, this test is not routinely ordered to diagnose factor V deficiency. A factor V inhibitor panel should also be ordered.

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