Laboratory testing for von Willebrand disease: contribution of multimer analysis to diagnosis and classification.

The stepwise diagnosis of von Willebrand disease (vWD) includes patient and family history, screening procedures (bleeding time, filter tests, platelet counts, activated partial thromboplastin time [aPTT]), confirmatory tests (von Willebrand factor [vWF]:antigen [Ag], vWF:ristocetin cofactor activity assay [RCo], vWF:collagen-binding test [CB], ristocetin-induced platelet agglutination [RIPA], and factor [F] VIII:coagulant activity [C]) and tests for final classification (multimeric analysis, vWF:factor VIII binding, and platelet vWF). Accumulating knowledge of the different clinical phenotypes and the pathophysiological basis of the disease have been translated into a classification that differentiates between quantitative and qualitative defects by means of quantitative and functional parameters and by analyzing the electrophoretic pattern of vWF multimers, but without inclusion of the genotype. Recently, it has been shown that with a sensitive method of multimer analysis, a > 90% genotype-phenotype relation may be achieved in the near future.