Preanalytical issues that may cause misdiagnosis in haemophilia and von Willebrand disease.

von Willebrand disease (VWD) and haemophilia represent common inherited or acquired bleeding disorders, but many laboratories and clinicians continue to struggle with their diagnosis or exclusion. Difficulties in achieving a correct diagnosis or exclusion of VWD or haemophilia might be due to analytical issues. Sometimes assays may generate a wrong result (ie an analytical error) or may have limitations in their dynamic range of measurement and/or their level of low analytical sensitivity. Less well recognized is the influence of preanalytical issues on the diagnosis of VWD or haemophilia. Therefore, this narrative review aims to provide an overview of some important preanalytical aspects that may affect the diagnosis of VWD or haemophilia, as well as a range of solutions that may help in mitigating or abrogating their influence. The review includes discussion of the more commonly noted preanalytical issues, such as haemolysis/icterus/lipaemia, and sample collection, processing and transport. However, we also extensively discuss other less well-recognized preanalytical issues, including clinical requests, anticoagulants and anticoagulant therapy, and laboratory test choices to name a few.