What are causes of an isolated elevation of prothrombin time (PT) (normal activated partial thromboplastin time [aPTT])

By William Aird

Factor VII (FVII) deficiency, FVII inhibitor (rare), early vitamin K deficiency, vitamin K antagonist, chronic liver disease, and disseminated intravascular coagulation (DIC).

Liver disease and DIC affect multiple clotting factors in the extrinsic, intrinsic and common pathway. These conditions may be associated with isolated elevation of the PT because FVIII levels are often high (acute phase reactant, produced in endothelial cells), compensating for depletion of other factors in the intrinsic pathway.

Isolated elevation in PT. Primary cause is deficiency of or inhibitor against factor VII (red). DIC, disseminated intravascular coagulation.