Which laboratory test is used to diagnose von Willebrand disease?

The diagnosis of von Willebrand disease primarily involves evaluating the function and quantity of von Willebrand factor (vWF), which is essential for normal platelet function and plays a critical role in hemostasis. Platelet aggregation studies are specifically designed to assess how well platelets clump together in response to different agonists, which is a crucial aspect of the bleeding disorder seen in patients with von Willebrand disease.

In von Willebrand disease, the impairment in platelet function or the deficiency in von Willebrand factor can be revealed through these studies, as they measure how effectively platelets aggregate when exposed to specific stimuli. The aggregation response can be abnormal, indicating the presence of this bleeding disorder.

Other tests, while useful in evaluating coagulation and hemostasis, do not specifically diagnose von Willebrand disease. For example, prothrombin time is used primarily to evaluate the extrinsic pathway of coagulation and may not reveal the issues related to vWF. Activated partial thromboplastin time assesses the intrinsic pathway and can be prolonged in various conditions but is not specific for von Willebrand disease. Thrombin time measures the time it takes for a thrombus to form, primarily assessing the common pathway of coagulation following the activation of prothrombin,