Laboratory Testing for von Willebrand Disease: The Past, Present, and Future State of Play for von Willebrand Factor Assays that Measure Platelet Binding Activity, with or without Ristocetin.

von Willebrand disease (VWD) was first described nearly a century ago in 1924 by Erik Adolf von Willebrand. Diagnostic testing at the time was very limited and it was not until the mid to late 1900s that more tests became available to assist with the diagnosis and classification of VWD. Two of these tests are based on ristocetin, one being ristocetin-induced platelet aggregation (RIPA) and the other the von Willebrand factor (VWF) ristocetin cofactor assay (VWF:RCo). The VWF:RCo assay provides functional assessment of in vitro VWF binding to the platelet glycoprotein (Gp) complex, GPIb-IX-V. Despite some advancements and newer technologies utilizing the principles of the original VWF:RCo assay, the original assay is still referred to as the gold standard for measurement of VWF activity. This article will review the history of VWD diagnostic assays, including RIPA and VWF:RCo over the past 40 years, as well as the newer assays that measure platelet binding with or without ristocetin, and which have been developed with the aim to potentially replace platelet-based ristocetin-dependent assays.