Stable factor; Proconvertin; Autoprothrombin I
The factor VII assay is a blood test to measure the activity of factor VII. This is one of the proteins in the body that helps the blood clot.
How to Prepare for the Test
You may need to temporarily stop taking some medicines before this test. Your health care provider will tell you which ones.
How the Test will Feel
When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or slight bruising. This soon goes away.
Why the Test is Performed
This test is used to find the cause of abnormal bleeding (decreased blood clotting). This decreased clotting may be caused by an abnormally low level of factor VII.
The normal value is 50% to 200% of the laboratory control or reference value.
Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or may test different samples. Talk to your provider about the meaning of your specific test results.
What Abnormal Results Mean
Decreased factor VII activity may be related to:
Veins and arteries vary in size so it may be harder to take a blood sample from one person than another. Other slight risks from having blood drawn are may include:
- Excessive bleeding
- Fainting or feeling lightheaded
- Hematoma (blood accumulating under the skin)
- Infection (a slight risk any time the skin is broken)
This test is most often done on people who have bleeding problems. The risk of excessive bleeding is slightly greater than for people without bleeding problems.
Chernecky CC, Berger BJ. Factor VII (stable factor, proconvertin, autoprothrombin I) - blood. In: Chernecky CC, Berger BJ, eds. Laboratory Tests and Diagnostic Procedures. 6th ed. St Louis, MO: Elsevier Saunders; 2013:503-504.
Schmaier AH. Laboratory evaluation of hemostatic and thrombotic disorders. In: Hoffman R, Benz EJ Jr, Silberstein LE, Heslop HE, Weitz JI, Anastasi J, eds. Hematology: Basic Principles and Practice. 6th ed. Philadelphia, PA: Elsevier Saunders; 2013:chap 131.