VTNE Laboratory Procedures Practice Test

Von Willebrand disease primarily impairs primary hemostasis and mucosal bleeding, so a presurgical screen should directly assess platelet function and the tendency to bleed from mucosal surfaces. The buccal mucosal bleeding time measures how long it takes for bleeding to stop after a standardized mucosal injury, reflecting platelet adhesion and plug formation that depend on von Willebrand factor. In von Willebrand disease, defective platelet adhesion prolongs this bleeding time, making it a sensitive screening test for mucosal bleeding disorders before surgery.

Total platelet count looks at how many platelets are present but doesn’t tell you how well they function; platelet numbers can be normal even when function is impaired. Activated clotting time and activated partial thromboplastin time assess the coagulation cascade (secondary hemostasis) and may be normal in many cases of von Willebrand disease, so they’re less specific for detecting this condition as a preoperative screen.