Comparison of an automated chemiluminescent assay to a manual ELISA assay for determination of von Willebrand Factor collagen binding activity on VWD plasma patients previously diagnosed through molecular analysis of VWF.

INTRODUCTION: The correct diagnosis and classification of VWD (von Willebrand disease) is crucial and must be optimized by including the collagen binding assay (VWF:CB). VWF:CB remains an under-recognized tool, not fully automated. The objective of this study was to evaluate and to compare the previously evaluated automated chemiluminescent assay (HemosIL AcuStar VWF:CB) to the ELISA ASSERACHROM® assay used routinely in our laboratory in patients with molecular diagnosis of VWD. METHODS: A plasma sample from 49 patients previously diagnosed with VWD (type 1; type 2A, type 2M, type 2B) through phenotype and VWF (von Willebrand factor) analysis and 15 healthy controls was analysed. The VWF ristocetin cofactor activity (VWF:Rco) and VWF antigen (VWF:Ag) were performed simultaneously on the VWD plasma samples, and VWF:CB/VWF:Ag ratios were calculated. RESULTS: The AcuStar VWF:CB assay was quickly performed with Pearson's correlation coefficient (r²) of .9571 between assays and a bias of +5.1U/dL (AcuStar > ELISA). Discrepancies of VWF:CB/VWF:Ag ratio were observed in type 2M-2A-like VWD (ratio <0.6 with AcuStar assay in 4/5 samples). CONCLUSION: The AcuStar VWF:CB assay has demonstrated good performance to detect VWF mutational changes with capacity to discriminate quickly principal types of VWD.