Assessment of the Von Willebrand Factor Multimers Profile in Patients Referred for Bleeding Tendency Evaluation in Estonia: A Preliminary Report of the Von Willebrand Disease Diagnostics Project

Introduction: VonWillebrand disease (VWD) is considered the most common autosomal inherited bleeding disorder. Laboratory testing for diagnosis or exclusion of VWD is based on a complex of different diagnostic assays. In the diagnostic workup of patients with suspected VWD, the von Willebrand factor (VWF) multimer assay is one of the most important indicators for VWF quality. This study aims to assess the VWF multimers profile in patients with bleeding tendency and increase knowledge and awareness of VWD laboratory diagnosis in Estonia. Methods: This retrospective study investigated the laboratory results of 131 individuals who were selected from the laboratory information system based on the request of VWF tests profile and 31 healthy volunteers for comparison. Results: Control group, non-VWD patients and patients suspected with VWD type 2N or mild haemophilia A demonstrated normal VWF multimer (VWF:MM) pattern. Patients with low VWF and suspected with VWD type 1 also showed normal VWF:MM distribution with reduced intensity. All cases suspected with VWD type 2A or 2M had a decrease of high molecular weight multimers (HMWM); one of them showed a loss of intermediate molecular weight multimers and HMWM and low VWF activity to antigen ratio (<0.7). Furthermore, multimers were undetectable in patients suspected with VWD type 3 or severe type 1. Conclusions: This is the first report of VWD laboratory evaluation in Estonia to provide insight into the potential clinical significance of using VWF: MM. The interpretation of VWF multimers should be necessarily complemented by the quantification of fractions of multimers by densitometry additional to visual gel's examination.