title: Laboratory diagnosis and management of von Willebrand disease in South Africa.
abstract: Patients with  Von Willebrand disease (VWD) in South Africa are cared for in 17 Hemophilia Treatment Centers. The exact prevalence of the disease is uncertain, but 539 patients are annotated in registries. VWD patients are mostly diagnosed in the five largest academic centers, and the classification of the subtypes is performed by one of these, the VWD testing facility. An algorithm is used for the diagnosis of VWD. The distribution of subtypes diagnosed by the VWD reference center is 38%, 58%, and 4% for type 1, 2, and 3, respectively, and ~15% of plasma samples received are rejected due to poor storage and transport conditions. A novel single nucleotide polymorphism has been found in an African patient with type 2B VWD. From the type 1 VWD patients who were diagnosed by the VWD testing facility, 45% seem to have an increased VWF clearance phenotype with a propeptide-to-antigen ratio of 1.9 ± 0.3. VWD patients are treated with desmopressin, factor (F)VIII/VWF concentrate (Haemosolvate FVIII; National Bioproducts Institute, Durban, South Africa), and tranexamic acid. Haemosolvate FVIII contains a VWF antigen concentration of 167 ± 27 IU/mL, a ristocetin cofactor activity of 100 ± 29 IU/mL, a collagen binding activity of 99 ± 29 IU/mL, normal VWF multimers, and a FVIII concentration of 50 IU/mL. Not all patients with VWD are currently classified, and many VWD patients in South Africa are probably undiagnosed.
authors.affiliation: Department of Haematology and Cell Biology, University of the Free State and NHLS, Bloemfontein, South Africa. gnhmsmm@ufs.ac.za
authors.forename: Muriel
authors.initials: M
authors.lastname: Meiring
authors.forename: Marius
authors.initials: M
authors.lastname: Coetzee
authors.forename: Mareli
authors.initials: M
authors.lastname: Kelderman
authors.forename: Philip
authors.initials: P
authors.lastname: Badenhorst
mesh_terms: D000465:Algorithms; D019411:Clinical Laboratory Techniques / Q000379:methods*; D003029:Coagulants / Q000627:therapeutic use*; D003894:Deamino Arginine Vasopressin / Q000627:therapeutic use; D005169:Factor VIII / Q000627:therapeutic use; D005820:Genetic Testing; D006801:Humans; D009154:Mutation; D014842:von Willebrand Diseases / Q000175:diagnosis* / Q000188:drug therapy* / Q000235:genetics; D014841:von Willebrand Factor / Q000235:genetics / Q000627:therapeutic use
chemical_list: D003029:Coagulants; D014841:von Willebrand Factor; D005169:Factor VIII; D003894:Deamino Arginine Vasopressin