Hemostasis Reference Laboratory

Factor VIII Activity

• Transaction Code: 3210-13
• CPT Code (Suggested): 85240

A one-stage intrinsic system clotting assay is used to measure circulating factor VIII levels. Clotting times of dilutions of patient plasma are compared to dilutions of a plasma pool from normal donors, when added to deficient plasma. Levels are reduced by hereditary (Hemophilia A) or acquired factor VIII deficiency, factor VIII inhibitors, von Willebrand disease, or disseminated intravascular coagulation (DIC). Levels may also be reduced or borderline in female carriers of Hemophilia A. Since factor VIII is an acute phase reactant, levels are elevated by stress, inflammation, surgery, exercise, pregnancy, or estrogen therapy.

• Sample Required: 0.5 ml frozen plasma x4 or (2) 3.2% sodium citrated tubes, 5 ml each.
• See Sample Requirements when ordered with other tests.
• Normal Range: 54-152%, effective 3/1/12
• Analytic Time: Within 3 working days, available STAT (see VWD panel for analytic time when ordered as VWD panel)