Laboratory diagnosis of von Willebrand disease: The phenotype

Von Willebrand disease (VWD) is one of the most common congenital bleeding disorders. Although laboratory values below the reference range will be detected in about 1% of the population, the prevalence of true VWD is much lower. Therefore, clinical observation is necessary for differentiation between a purely laboratory phenomenon versus a clinically relevant disease. For the diagnosis and classification of VWD, a battery of tests is necessary. These are usually classified as screening diagnostic tests, extended diagnostic tests, and special diagnostic tests. Screening diagnostic tests have low sensitivity and specificity but are valuable tools for ruling out VWD and may help diagnose another defect of primary hemostasis. The extended diagnostic tests can usually confirm the diagnosis of VWD, while the special diagnostic tests are valuable tools in classifying the disease. In some cases the diagnosis cannot be proven without performing a subset of the special diagnostic tests. Thus, usually a battery of tests has to be performed until a patient with a defect of primary hemostasis can be diagnosed with acceptable certainty.