•Specific clotting factor assays will be done after a platelet count, aPTT, and PT are done for screening.
•Clotting factor assays must be done to confirm diagnosis.
•Most forms of hemophilia are caused by deficiency of factor VIII or factor IX.
•With hemophilia, the platelet count and prothrombin time are normal. aPTT is generally elevated, but may be normal, this is why factor assays are done.