A platelet function test is often the first screening test for patients with suspected VWD. The platelet function test can be important in helping to verify the efficacy of desmopressin acetate (DDAVP) therapy. DDAVP is a synthetic analog of the hormone ADH (antidiuretic hormone, also known as vasopressin). In addition to its renal effects, DDAVP stimulates the release of VWF from endothelial cells. Therefore, it can be used to increase circulating levels of VWF (as well as factor VIII). DDAVP is used in VWD, mild hemophilia A (factor VIII deficiency), and thrombocytopenia. The usefulness of DDAVP is limited to VWD patients with quantitative (decreased) levels of VWF. In patients who have functional defects in VWF, it is ineffective since it would only increase circulating levels of the nonfunctional protein.
After an initial platelet screening test, a more extensive panel can be ordered to diagnose VWD. This panel would include an aPTT, factor VIII activity assay, VWF antigen, and VWF activity.
