Rethinking internal quality control and external quality assessment for laboratory diagnostics of von Willebrand disease

Emmanuel J. Favaloro


von Willebrand disease (VWD) is recognised as the most common congenital bleeding disorder, and an acquired form named von Willebrand syndrome (AVWS) may arise in a variety of disease states. Thus, laboratory testing for VWD and AVWS represents a key diagnostic activity of hematology facilities performing advanced hemostasis diagnostics. VWD and AVWS arise due to deficiency and/or defect(s) in the adhesive plasma protein called von Willebrand factor (VWF). VWF represents a key element of primary hemostasis, and also contributes to secondary hemostasis. Thus, deficiency and/or defects in VWF, either congenital or acquired, leads to a bleeding diathesis in affected individuals. A wide variety of laboratory tests may be performed to investigate, diagnose or exclude VWD/AVWS, including screening assays, more complex functional assays, and also molecular analysis. Thus, VWD testing now incorporates a variety of processes, and potential methodologies. Internal quality control (IQC) and external quality assessment (EQA) is critical to ensure the quality of laboratory testing, but is made difficult in VWD diagnostics by the nature and variety of the tests available, and the heterogeneity of VWD/AVWS. The current review looks at laboratory testing for VWD/AVWS from the perspective of IQC and EQA, and considers some novel approaches to ensure the accuracy and quality of this activity in the future diagnostics landscape.