A prolonged PT may indicate which of the following?

A prolonged PT may indicate which of the following?

• A. Intrinsic pathway abnormalities.
• B. Factor VIII deficiency.
• C. Diabetic ketoacidosis.
• D. Warfarin therapy.

Answer: (D)

Prothrombin time (PT) assesses the extrinsic pathway and the common pathway of coagulation, primarily reflecting the activity of factors II, VII, IX, and X, with factor VII (having the shortest half-life) making PT sensitive to changes in this route. Warfarin inhibits vitamin K–dependent synthesis of these factors, especially those in the extrinsic pathway, so PT becomes prolonged when someone is on warfarin. That timing and mechanism is why warfarin therapy is the scenario that would show a prolonged PT. Intrinsic pathway abnormalities and Factor VIII deficiency mainly affect another test, the activated partial thromboplastin time (aPTT), not PT. Diabetic ketoacidosis does not typically cause a prolonged PT as a direct hallmark.

Prothrombin time (PT) assesses the extrinsic pathway and the common pathway of coagulation, primarily reflecting the activity of factors II, VII, IX, and X, with factor VII (having the shortest half-life) making PT sensitive to changes in this route. Warfarin inhibits vitamin K–dependent synthesis of these factors, especially those in the extrinsic pathway, so PT becomes prolonged when someone is on warfarin. That timing and mechanism is why warfarin therapy is the scenario that would show a prolonged PT.

Intrinsic pathway abnormalities and Factor VIII deficiency mainly affect another test, the activated partial thromboplastin time (aPTT), not PT. Diabetic ketoacidosis does not typically cause a prolonged PT as a direct hallmark.