Which laboratory test would likely be prolonged in a patient with liver disease?

In a patient with liver disease, the prothrombin time (PT) is likely to be prolonged due to the liver's essential role in synthesizing coagulation factors, particularly those involved in the extrinsic pathway, such as factors I (fibrinogen), II (prothrombin), V, VII, and X. In liver dysfunction, the production of these factors is impaired, leading to a decrease in their levels, which subsequently results in a longer time for the blood to clot.

Additionally, the prothrombin time is often used as a marker for liver function, as it reflects the liver's capability to produce clotting factors. Since PT measures the extrinsic and common pathways of coagulation, it becomes an important test in assessing coagulopathy associated with liver disease.

While activated partial thromboplastin time (aPTT) may also be prolonged in liver disease due to deficiencies in the intrinsic pathway factors (like factors VIII, IX, XI, and XII), PT is specifically sensitive to the liver's synthetic capacity regarding factors that are produced there. The international normalized ratio (INR) is derived from the PT and similarly reflects the same process. Therefore, both PT and INR would be prolonged in liver disease,