Which test pattern is typical of hemophilia?

Which test pattern is typical of hemophilia?

• A. Normal BT, PT, aPTT
• B. Increased aPTT with normal BT and PT
• C. Prolonged PT with normal aPTT
• D. Increased BT with prolonged PT

Answer: (B)

Hemophilia affects the intrinsic pathway of coagulation, so the test that measures that pathway is prolonged, while the extrinsic pathway and primary hemostasis stay normal. The activated partial thromboplastin time (aPTT) assesses the intrinsic and common pathways, so it becomes prolonged when factor VIII or IX is deficient. The prothrombin time (PT) tests the extrinsic pathway and should remain normal, and bleeding time reflects platelet function, which is not impaired in classic hemophilia. Therefore, the typical pattern is an increased aPTT with normal PT and normal bleeding time.

Hemophilia affects the intrinsic pathway of coagulation, so the test that measures that pathway is prolonged, while the extrinsic pathway and primary hemostasis stay normal. The activated partial thromboplastin time (aPTT) assesses the intrinsic and common pathways, so it becomes prolonged when factor VIII or IX is deficient. The prothrombin time (PT) tests the extrinsic pathway and should remain normal, and bleeding time reflects platelet function, which is not impaired in classic hemophilia. Therefore, the typical pattern is an increased aPTT with normal PT and normal bleeding time.