American Board of Internal Medicine (ABIM) Certification Practice Exam

Which laboratory result is expected in liver failure coagulopathy?

1. Elevated activated partial thromboplastin time

2. High factor X levels

3. Normal fibrinogen levels

4. Normal prothrombin time

The correct answer is: Elevated activated partial thromboplastin time

In the context of liver failure coagulopathy, an elevated activated partial thromboplastin time (aPTT) is expected. The liver plays a crucial role in producing many of the clotting factors necessary for hemostasis, including factors II, V, VII, IX, and X. Liver failure often leads to a deficiency in these clotting factors due to impaired synthesis. As several of the factors involved in the intrinsic pathway of coagulation are produced in the liver, a failure to produce these factors results in a prolonged aPTT. This reflects the underlying coagulopathy associated with liver dysfunction, particularly as factors VIII and XII, which are also involved in the intrinsic pathway, may still be present but are not produced in sufficient quantities due to liver disease. In this context, high factor X levels would not be expected, as liver failure generally leads to decreased levels of clotting factors, including factor X. Similarly, abnormal fibrinogen levels may also be present in liver failure; fibrinogen can become low due to liver dysfunction. Normal prothrombin time would not be expected either, as prothrombin—produced by the liver—will typically be prolonged in cases of liver failure due to the reduction in the