Glycoprotein 1bM assay and von Willebrand disease: a change in diagnosis

The diagnosis of von Willebrand disease (VWD) is complicated by limitations of traditional laboratory tests, such as the VWF ristocetin cofactor (VWF:RCo) assay. Newer assays, such as the VWF glycoprotein 1bM (VWF:GP1bM) assay, are more reliable and not affected by the D1472H polymorphism; thus, current hematology societal guidelines recommend these newer assays for diagnosing VWD. This study aims to perform a descriptive analysis of the impact of the VWF:GP1bM assay on the diagnosis of VWD among previously diagnosed patients at the Hemophilia Center of Western Pennsylvania. This retrospective chart review included patients with a historical diagnosis of VWD, in part based on VWF:RCo activity, VWF:GP1bM activity performed separate from and subsequent to the historical diagnosis of VWD, and 18 years of age at the time of data abstraction. The primary outcome was a change in historical VWF:RCo assay-based diagnosis to an alternative current VWF:GP1bM assay-based diagnosis. This study analyzed 138 patients with a mean age of 36.7 years. The mean VWF:RCo activity, 0.56 IU/ml, was lower than the mean VWF:GP1bM activity, 0.73 IU/ml, P < 0.001. The VWF:GP1bM assay led to a change in diagnosis in 42.8% of patients, including 26.1% of patients with no bleeding disorder. The presence of the D1472H polymorphism was associated with 10.6 greater odds, P < 0.01, of a change in diagnosis. The use of the VWF:GP1bM assay may improve the ability to accurately diagnose VWD, prompting a change in diagnosis and emphasizing the assay's critical role in optimizing patient care.