Description
Evaluating Abnormal Clotting Due to Factor VII Inhibition
What is this test?
The Factor VII Inhibitor Reflex Titer is a specialized blood test used to identify and measure antibodies that interfere with Factor VII, a vital protein involved in blood clotting. These antibodies are called inhibitors, and they can reduce the activity of Factor VII, increasing the risk of bleeding disorders.
This test is reflexive—meaning it is only performed if an initial Factor VII activity test shows decreased levels. If inhibition is detected, the Bethesda assay is used to determine the strength (titer) of the inhibitor.
Why this test may be ordered:
- To evaluate unexplained bleeding or prolonged clotting times
- To investigate low Factor VII activity found during routine or preoperative testing
- To monitor known bleeding disorders or inhibitor development in patients with acquired or congenital Factor VII deficiency
- To differentiate between a true deficiency and an inhibitor-related decrease
Conditions that may cause low Factor VII activity:
- Liver disease (hepatic dysfunction)
- Vitamin K deficiency
- Use of blood thinners like warfarin (coumarin therapy)
- Congenital Factor VII deficiency
- Presence of specific Factor VII inhibitors (autoantibodies)
- Rare metabolic or bone marrow disorders, such as:
- Homocystinuria
- Aplastic anemia
How the Reflex Titer Works:
- Initial Factor VII activity assay is performed.
- If activity is normal or elevated, a technical comment is reported.
- If activity is decreased, an inhibitor screen is performed.
- If a specific inhibitor is detected, the titer is quantified using the Bethesda method.
Fasting not required.
