Superiority of the Rapid Von Willebrand Factor (VWF) VWF:GPIbR and VWF:GPIbM Assays in Type 2A, 2B and 2M Von Willebrand Disease

A complete set of rapid activity and classical von Willebrand factor (VWF) assays for Willebrand disease (VWD) diagnosis was used in the present study to characterize VWD type 1, 2A, 2B and 2M patients due to mutations in the A1, A2 and A3 domains. The VWF:RCo/VWF:Ag, VWF:GPIbM/VWF:Ag and VWF:GPIbR/VWF:Ag ratios at cuttt off value of 0.7 separated VWD type 1 and LowVWF from VWD type 2. The results from the Brno cohort of VWD 2A patients with the G1579R mutation in the A2 domain in sixteen affected member from five families and in one case with the G1609R in the A2 domain revealed that the VWF:GPIbM/VWF:Ag and VWF:GPIbR/VWF: Ag ratios are marked decreased (range 0.03-0.27) to a similar degree as compared to VWF:RCo/VWF:Ag and VWF:CB/VWF:Ag ratios (range 0.03-0.27) due to the proteolytic loss of large and intermediate VWF multimers. The results in VWD 2B patients due to gain of ristocetin induced platelet agglutination (RIPA) function mutations R1306W, R1308C and R1341 in the A1 domain demonstrated that the ratios for VWF:GPIbM/VWF:Ag and VWF:GPIbR/VWF:Ag as compared to VWF:RCo/VWF:Ag ratio were markedly decreased in VWD 2B, whereas the VWF:GPIbM/VWF:Ag ratio was somewhat higher (range 0.32 to 0.36) in VWD 2M. VWD 2M patients due to loss of RIPA function mutation R1359K in the A1 domain are featured by decreased VWF ratios for WVF:RCo/Ag and VWF:GPIbR/Ag, but less decreased for the VWF:GPIbM/Ag ratio and normal VWF ratio for VWF:CB/Ag ratio the need to retain the VWF:CB assay to make a correct diagnosis of VWD 2M for its differentiation from VWD type 1. The G1415D mutation in the A1 domain is featured by decreased RIPA and decreased VWF:RCo/VWF:Ag ratio (VWD 2M) but normal values for VWF:CB/VWF:Ag, VWF:GPIbM/VWF:Ag and VWFGPIbR/VWF:Ag ratios consistent with VWD 2M. Double heterozygous P1266L/V1278I mutation in two patients and heterozygous E1292D/WT mutation in three patients in the A1 domain were diagnosed as VWD 2M or 1M associated with a secretion defect (SD). The Platelet Function Analyzer Closure Times (PFA-CT) are strongly prolonged in VWD 2A, 2B and 2M. and moderately prolonged between the upper limit of normal to 300 seconds in heterozygous mutated VWD type 1 patients.