Factor VIII, also known as anti-hemophilic factor, is an essential blood-clotting factor that is deficient or absent in people with hemophilia. It is a protein that brings about the conversion of prothrombin to thrombin, which in turn creates fibrin fibers round which a blood clot forms. It is extracted from blood plasma or genetically engineered and used for treating hemophilia.

 

Factor VIII assay

The factor VIII assay is a blood test that measures the activity of factor VIII. Blood is typically drawn from a vein, usually from the inside of the elbow or the back of the hand. In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip.

 

A normal value is 50–200% of the laboratory control or reference value. Normal value ranges may vary slightly among different laboratories.