Evaluation of an heterogeneous group of patients with von Willebrand disease using an assay alternative to ristocetin induced platelet agglutination

Summary Background Diagnosis of von Willebrand disease (VWD) type 2 usually relies on the discrepancy between the von Willebrand factor (VWF) ristocetin cofactor activity (VWF:RCo) and VWF antigen (VWF:Ag). Type 2B patients can be discriminated from other qualitative VWD variants by using ristocetin‐induced platelet agglutination (RIPA) test. The major limitation of RIPA is the requirement of fresh blood sample. Objectives In this study, we evaluated the VWF gain‐of‐function mutant GPIb binding (VWF:GPIbM) and VWF:RCo assays to investigate whether the VWF:GPIbM/VWF:RCo ratio was able to identify the type 2B variant among an heterogeneous VWD population, previously characterized following the ISTH‐SSC guidelines. Patients/methods Seventy‐six VWD patients and 31 healthy subjects were evaluated by using VWF:Ag, VWF:RCo, and VWF:GPIbM assays. Results The mean (minimum–maximum values) VWF:GPIbM/VWF:RCo ratio was higher in type 2B patients (2.53, 0.84–6.11) than in healthy controls (1.05, 0.87–1.34), type 1 (0.85, 0.51–1.15), 2A (1.20, 0.36–2.82), and 2M (1.07, 0.91–1.38) (P