Assay of the following blood clotting factors are commercially available:

Clotting Factor Assays

• Factor I, Fibrinogen
• Factor II, Thrombin
• Factor II, 20210 Mutation
• Factor V, Labile Factor/Proaccelerin
• Factor V, R506Q Leiden
• Factor VII, Stable Factor/Proconvertin
• Factor VIII, Antihemophilia Factor
• Factor VIII R:AG, von Willebrand Factor
• Factor IX, Antihemophilia Factor B/Christmas Factor
• Factor X, Stuart Factor
• Factor XI, Antihemophilia Factor C/Plasma Thromboplastin Antecedent
• Factor XII, Hageman Factor
• Factor XIII, Fibrin Stabilizing Factor
• Protein C
• Protein S

The majority of these assays measure functional activity in various clotting tests employing factor deficient plasma.

Factor VIII and Factor VIIIR antigen assays are employed in the diagnosis and management of hemophilia A and von Willebrand patients, and are described under their respective headings. Factor IX assays are used in the diagnosis and management of hemophilia B patients.

Fibrinogen levels and protein C and protein S assays are occasionally useful in patients with unexplained thrombosis. Factor II (20210 mutation) and Factor V (Leiden) are diagnosed by molecular techniques in patients with unexplained thrombosis.

The other factor assays are of limited use in general clinical practice and performance is limited to the more specialized coagulation laboratories.