disease (VWD) is reportedly the most common inherited bleeding disorder, potentially affecting up to 1% of the population according to epidemiologic data, although numbers based on presentation to clinics are closer to 0.1%. 1 VWD arises from defects and/or deficiency of von Willebrand factor (VWF), and laboratory testing assists clinical exclusion or diagnosis. [2][3][4][5] Contemporary laboratory assays comprise VWF antigen (VWF:Ag), markers of VWF activity, and factor VIII activity (FVIII:C), 2-7 using various methods.There are many VWF activity assays, especially those reflective of glycoprotein Ib (GPIb) binding (including classical ristocetin cofactor [VWF:RCo]), and for which the VWF/VWD Scientific Standardisation Committee (SSC) of the ISTH has recommended revised nomenclature. 5,7 VWF:RCo assays using platelets, ristocetin, and native GPIb remain VWF:RCo, but those using other solid-phase particles and recombinant GPIb are termed VWF:GPIbR. 5,7 Additional gainof-function VWF assays using recombinant GPIb mutations reflect VWF:GPIb binding assays similar to VWF:RCo and VWF:GPIbR but that do not employ ristocetin are termed VWF:GPIbM. 5,7-9 Another distinct category of VWF activity assay is the collagen binding assay (VWF:CB). 5,10 Assessment of VWF multimers by gel electrophore-This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.