Part 1: von Willebrand Disease: Approach to Diagnosis and Management
Natalia Rydz, MD
Clinical Assistant Professor, Division of Hematology and Hematologic Malignancies, Foothills Medical Centre, Calgary AB, Canada
A 30-year-old man presents with prolonged bleeding after a dental extraction. Mild hemophilia A is suspected based on a baseline factor VIII (FVIII) level of 9 IU/dL. Further testing reveals the following: genotyping is negative for a F8 mutation; a desmopressin (DDAVP) trial shows a brisk but short-lived FVIII response; von Willebrand factor antigen (VWF:Ag) level is 0.55 IU/dL and VWF ristocetin cofactor (VWF:RCo) is 0.50 IU/dL.
What is the next most useful test?