What coagulation test results are indicative of Vitamin K deficiency?

Vitamin K deficiency primarily affects the synthesis of certain clotting factors in the liver, specifically factors II (prothrombin), VII, IX, and X, which are critical for the coagulation cascade. The prothrombin time (PT) is particularly sensitive to deficiencies in these factors because it assesses the extrinsic pathway and common pathway of coagulation, where these Vitamin K-dependent factors operate.

When Vitamin K levels are insufficient, the prothrombin time will be prolonged, indicating a high value for PT. The activated partial thromboplastin time (APTT), which evaluates the intrinsic pathway, may remain normal in early stages of Vitamin K deficiency, as it is less affected since it does not primarily depend on the factors II and VII as much as the extrinsic pathway does.

Thus, elevated PT along with normal or minimally affected APTT results would suggest Vitamin K deficiency. The combination of high PT and potentially normal or slightly elevated APTT aligns with this condition, effectively pointing to the vitamin's critical role in clotting factor synthesis and its implications in bleeding disorders associated with vitamin deficiencies.