In von Willebrand disease (vWD), which tests show elevated results?

In von Willebrand disease (vWD), the most significant abnormality observed in laboratory tests is the prolongation of the activated partial thromboplastin time (APTT), along with an increased bleeding time.

The reason APTT is often elevated in vWD is that von Willebrand factor (vWF) plays a crucial role in stabilizing factor VIII, which is essential for the intrinsic pathway of coagulation. When vWF is deficient or dysfunctional, as is the case in vWD, factor VIII levels can decrease, leading to a longer APTT.

Bleeding time is also prolonged in vWD due to the impaired platelet function, as vWF is vital for platelet adhesion to the injured vascular wall. A deficiency of vWF results in ineffective platelet aggregation, which contributes to the increased bleeding time observed in patients.

While other tests like prothrombin time (PT) may remain normal, the combination of prolonged APTT and bleeding time is indicative of von Willebrand disease and reflects the underlying defect in both clotting factor stability and platelet function. This understanding is critical in recognizing and diagnosing von Willebrand disease effectively.