What is a classic sign of Vitamin K deficiency in coagulation results?

A classic sign of Vitamin K deficiency in coagulation results is reflected in the elevation of both Prothrombin Time (PT) and Activated Partial Thromboplastin Time (APTT). Vitamin K is essential for the synthesis of several clotting factors (specifically factors II, VII, IX, and X) in the liver. A deficiency in Vitamin K leads to impaired production of these clotting factors, which in turn prolongs both PT and APTT on coagulation testing.

When Vitamin K levels are low, the PT is typically elevated first because factor VII has the shortest half-life among the vitamin K-dependent factors, which means it will be affected more quickly by low Vitamin K levels. However, as the deficiency progresses, other factors that are also dependent on Vitamin K will start to be produced insufficiently, leading to a concurrent elevation in APTT. Therefore, the presence of a high PT alongside a high APTT indicates that the body is unable to properly initiate and sustain coagulation due to a lack of these crucial factors, characteristic of Vitamin K deficiency.

In contrast, an isolated prolongation of PT with a normal APTT or changes in bleeding time do not specifically indicate Vitamin K deficiency and may suggest other coagulation disorders