Comparison of a new chemiluminescent immunoassay for von Willebrand factor activity with the ristocetin cofactor‐induced platelet agglutination method

Summary. Measuring von Willebrand factor (VWF)activity is essential for the diagnosis of von Willebranddisease (VWD). The VWF activity is usually assessedbased on measurement of the ristocetin cofactor (VWF:RCo). However, that test is technically challenging andhas high intra- and inter-assay variabilities. A newautomated chemiluminescent immunoassay VWFactivity has recently become commercially available(HemosIL AcuStar von Willebrand Factor RistocetinCofactor Activity). The main objective of this study wasto evaluate this new method and to compare it with theVWF:RCo assay as the reference method. We studied91 samples, 18 healthy volunteers samples and 73samples from patients (VWF:RCo level <50 IU dL 1 ):29 type 1 VWD, 13 type 2A, 5 type 2B, 5 type 2M, 3type 2N, 5 type 3, 4 type 3 under treatment, 5 type 3carriers and 4 samples with other pathologies. TheHemosIL AcuStar VWF:RCo assay was 96% sensitiveand 100% specific for detecting VWF abnormalities.The good analytical performance, and the sensitivityand specificity of HemosIL AcuStar VWF:RCo to detectVWF deficiency renders it a suitable method for VWDscreening.Keywords: chemiluminescence, ristocetin cofactor activity,von Willebrand disease, von Willebrand factor activity.