The efficacy of the two von Willebrand factor (vWF) intron 40 variable number of tandem repeat (VNTR) markers, vWF1 and vWF2, in the genetic diagnosis of von Willebrand disease (vWD) in Indian patients was studied. Three hundred and sixty-five unrelated normal individuals and 100 vWD patients (type 1: 18; type 2: 21; type 3: 61) were analyzed for the two vWF intron 40 VNTR markers. Polymerase chain reaction of the two markers vWF1 and vWF2 was done using specific primers followed by electrophoresis on 10% polyacrylamide gel. VNTR analysis revealed the presence of VNTR9 and VNTR15 along with the eight alleles VNTR6 to VNTR14 in the vWF1 marker. Furthermore, apart from the six alleles, VNTR1 to VNTR6 of the vWF2 marker, two new alleles, VNTR7 and VNTR8, were also found. The heterozygosity rates were 75 and 74% for vWF1 and vWF2, respectively. Overall, the heterozygosity rate, i.e. when both vWF1 and vWF2 were considered in combination, was 81%. These data were successfully applied for the detection of carriers in 10 severe type 3 vWD families. The high heterozygosity of the two vWF intron 40 VNTR markers and the simplicity of the technique without much cost being involved suggest the practical feasibility of this technique in developing countries like India.
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