Factor VII

Factor VII is one of the Vitamin K-dependent clotting proteins. It has an extremely important function as a ligand for Tissue Factor to initiate the clotting process after injury. FVII deficiency is therefore associated with serious bleeding, which includes bleeding from mucous membranes, epistaxis, excessive bruising, menorrhagia, and bleeding into muscles and joints.

Bleeding episodes can be controlled with normal plasma, concentrates containing Factor VII, or recombinant Factor VII. During bleeding episodes, frequent treatment is needed because the life span of Factor VII is short. Menstrual bleeding can be controlled by the use of oral contraceptives

FVII has the shortest half life (~3 hours) of all the clotting factors. Since it is produced by the liver, decreasing FVII levels are an early indicator of liver dysfunction. The Hemostasis and Thrombosis Laboratory measure FVII levels in patients found to have low Protein C activity. As the two proteins have similar plasma half lives and are both Vitamin K-dependent, low values for both proteins indicate hepatic insufficiency or Vitamin K absence or antagonism, and therefore mitigate against a congenital Protein C deficiency.

On routine coagulation screening, FVII deficiency is suggested by the finding of a prolonged PT with a normal APTT. Congenital FVII deficiency is associated with hemophilia-like bleeding tendency. Acquired deficiencies occur in association with liver disease, vitamin K absence or antagonism (e.g. coumadin), and rarely in association with Amyloidosis. Rare inhibitors of FVII have been described.

Assays of the coagulation factors are functional measurements of the individual clotting proteins. They are measured by testing the ability of the patient's plasma to correct the clot time of a plasma known to be completely deficient in the clotting factor under test. By comparing the degree of correction with dilutions of a normal plasma, the actual clotting factor level of the test plasma can be calculated. Factor assays are either based on the Prothrombin Time (Factors II, V, VII and X) or the APTT (Factors VIII, IX, XI and XII).

The normal range for FVII activity in the Hemostasis and Thrombosis Laboratory is 65 - 160%.