To better define what a significant bleeding history is, a bleeding score (BS), accounting for both the number and the severity of the bleeding symptoms, may be useful. It has been suggested that BSs ≥3 and ≥5 in males and females, respectively, constitute useful cut-offs to identify adults for whom measuring VWF-related activities is worthwhile [4]. The diagnosis of VWD is then based on the presence of reduced (<40 U dL−1) VWF:RCo (or VWF:CB), with a further characterization of VWD type based on assessment of VWF:Ag, FVIII and multimer pattern. In general, VWF levels <30 U dL−1 are

strongly associated with significant clinical severity and the presence of mutations in the VWF gene in type 1 VWD [6, 7]. However, levels <40 U dL−1, in individuals who have relatives with similar CP-673451 ic50 levels, is a crucial clue for diagnosis of mild VWD [5], even when the bleeding history is milder and treatment usually involves avoidance NVP-BGJ398 mouse of antiplatelet drugs and the use of

antifibrinolytics. Paediatric cases should be evaluated using less stringent criteria, although a recent study using the bleeding questionnaire adopted for adults showed that the threshold score for a significant bleeding history is ≥2 [8]. Table 1 summarizes a practical multistep approach to diagnosis. The VWF:RCo activity explores the interaction of VWF with platelet glycoprotein Ib/IX/V and remains the reference method for measuring VWF activity. An abnormal VWF:RCo/VWF:Ag ratio (<0.6) usually indicates the presence of qualitative variants (type 2 VWD). VWF:CB results are particularly sensitive to VWD variants characterized by the absence of larger VWF multimers [9]. VWF:CB is often used as an alternative to multimeric analysis and VWF:CB/VWF:Ag ratio determinations appear useful

for distinguishing between type 1 and 2 VWD [9]. In an 上海皓元 important exception, rare VWD mutations in the A3 domain (W1745C and S1783A) with normal multimeric patterns show a low VWF:CB/VWF:Ag ratio [10]. In some of these patients, the diagnosis of VWD could be missed since VWF:RCo levels may be in the borderline range. The ristocetin-induced platelet aggregation (RIPA) assay using patient platelets explores the threshold ristocetin concentration which induces aggregation of patient platelet-rich plasma. Aggregation occurring at low concentrations identifies type 2B VWD cases, in whom desmopressin may cause thrombocytopenia [4]. This test is critical especially when multimeric pattern evaluation is not feasible. The evaluation of closure time (CT) with a PFA-100 (Platelet Function Analyzer; Siemens, Marburg, Germany) allows a rapid and simple determination of VWF-dependent platelet function at high-shear stress. This system is sensitive and reproducible for the detection of severe reductions in VWF, but it has a questionable role in the screening for mild VWF deficiencies and type 2N VWD [11].