Work

A screening assay for type 2B von Willebrand factor variants using an enzyme-linked immunosorbent assay based on recombinant wild-type glycoprotein Ib and ristocetin

Year: 2026

Type: article

Abstract: Background: Type 2B von Willebrand disease (VWD) is caused by gain-of-function variants in the A1 domain of von Willebrand factor (VWF), leading to increased platelet binding, loss of high-molecular-weight multimers, and sometimes thrombocytopenia. Conventional diagnosis relies on ristocetin-induced platelet agglutination or molecular testing. Aim: To evaluate an in-house enzyme-linked immunosorbent assay (ELISA) based on a recombinant glycoprotein Ib wild-type (rGPIb-WT) fragment and ristocetin, as a screening tool to identify first-time referral patients requiring further evaluation for possible type 2B VWD. Materials and Methods: exon 28 Sanger sequencing. Results: Twenty-six of 254 patients tested positive at least at 1 ristocetin concentration. Sixteen were considered candidates for type 2B VWD evaluation based on a VWF:GPIbR/VWF:Ag ratio <0.7 and/or an abnormal multimeric pattern. Type 2B variants were found in 12 of 16 sequenced patients. The remaining 10 patients showed ultra-large multimers or an increased proportion of high-molecular-weight multimers; 8 of these had a normal VWF:GPIbR/VWF:Ag ratio (>0.7). Discussion: The rGPIb-WT ELISA positivity may reflect type 2B variants or the presence of larger multimers. Integrated with conventional assays, positivity may guide type 2B-directed evaluation.

Source: Research and Practice in Thrombosis and Haemostasis

DOI: 10.1016/j.rpth.2026.106971