Review Question - QID 213432

This patient with deep bleeding who has an isolated increase in partial thromboplastin time that does not normalize in a mixing study most likely has a coagulation factor inhibitor autoantibody.

Bleeding disorders can be classified as defects in primary or secondary hemostasis. Primary hemostasis is characterized primarily by platelets and can be measured with bleeding time. Secondary hemostasis is characterized primarily by the coagulation cascade and can be measured using prothrombin time or partial thromboplastin time. An isolated increase in partial thromboplastin time is indicative of a defect in the intrinsic pathway of coagulation. This can either be caused by a factor deficiency such as hemophilia or production of an autoantibody that functions as a factor inhibitor. Mixing studies can be used to distinguish between these possibilities because autoantibodies will not normalize upon mixing with a factor replacement.

Incorrect Answers:
Answer 1: Deficiency in a coagulation factor would also present with an isolated increase in partial thromboplastin time; however, it would normalize upon a mixing study.

Answer 2: Deficiency of von Willebrand factor would present with an increase in bleeding time in addition to the elevated partial thromboplastin time.

Answer 3: A platelet defect would present with an increase in bleeding time rather than a change in coagulation cascade values.

Answer 5: Warfarin toxicity would present with an increase in prothrombin time that is not seen in this patient.

Bullet Summary:
Patients with a coagulation factor inhibitor will present with abnormally increased coagulation times that do not normalize with mixing studies.