Hemostasis Coagulation Practice Test

Factor XII deficiency prolongs laboratory tests of the intrinsic pathway (aPTT) but does not cause abnormal bleeding in real life. In vivo, hemostasis can proceed normally even without Factor XII, so most patients have a negative bleeding history. This makes the typical answer that there is no history of abnormal bleeding the best choice.

Heavy bleeding is not expected because Factor XII is not essential for initial hemostasis. Platelet count isn’t affected by this deficiency, so a low platelet count wouldn’t be expected. PT is usually normal because Factor XII is part of the intrinsic pathway (measured by aPTT), not the extrinsic pathway (measured by PT).