Hageman factor assay
The factor XII assay is a blood test to measure the activity of factor XII -- one of the substances involved in blood clotting.
A blood sample is needed. For information on how this is done, see: Venipuncture.
There is no special preparation needed for adults.
When the needle is inserted to draw blood, you may feel moderate pain, or only a prick or stinging sensation. Afterward, there may be some throbbing.
Your doctor may order this test if you had abnormal results on the partial thromboplastin time (PTT) blood-clotting test, or if one of your blood relatives was diagnosed with factor XII deficiency.
Gailani D, Neff AT. Rare coagulation factor deficiencies. In: Hoffman R, Benz EJ Jr., Shattil SJ, et al, eds. Hoffman Hematology: Basic Principles and Practice. 5th ed. Philadelphia, Pa: Churchill Livingstone Elsevier; 2008:chap 127.
Kessler C. Hemorrhagic disorders: Coagulation factor deficiencies. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 180.
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