A 19-year-old man is having recurrent bleeding occur in his knee when playing contact sports. He has no history of spontaneous bleeding, but his brother has similar problems. Consultation with a specialist reveals that he has "mild" hemophilia A. Which of the following factor abnormalities is consistent with this diagnosis?

In hemophilia A, there are decreased levels of functioning factor VIII. This can be due to reduced amounts of normal VIII, the presence of a functionally abnormal protein, or a combination of both. The activated partial thromboplastin time (APTT) is prolonged, and the prothrombin consumption test is abnormal. The prothrombin time, thrombin clotting time, and bleeding time are usually normal.