Abstract

Von Willebrand factor (VWF) is a complex multimeric, multifunctional glycoprotein. It plays a primary role in haemostasis by forming platelet plugs at sites of vascular injury. The biological breakdown of VWF is mediated by a metalloprotease, ADAMTS-13. Both proteins are important in normal coagulation. Deficiencies in gene and or protein of VWF are associated with von Willebrand disease and those of ADAMTS-13 are associated with thrombotic thrombocytopenic purpura. The plasma VWF varies with some non-genetic and genetic factors such as ABO phenotypes. We aimed at establishing a normal range for VWF: Ag, VWF: CB and ADAMTS-13 in adult Nigerian population .We investigated three hundred and sixty (360) plasmas. They comprised of one hundred and forty-eight (148) blood groups O, ninety-eight (98) group A, ninety-five (95) group B and nineteen (19) AB blood groups. Subjects were aged between 20 to 60 years and they all gave their consent in accordance with the declarations of Helsinki. We determined their full blood count, ABO blood grouping and VWF: Ag level, VWF: CBA and ADAMTS-13 activity. Data show mean ± 2 SD of VWF: Ag levels for blood group A (1.359 ± 0.17 IU/ml); B (1.338 ± 0.22 IU/ml); AB (1.326 ± 0.44 IU/ml); O (1.233 ± 0.27 IU/ml); non-O (1.323 ± 0.22 IU/ml) and 1.286 ± 0.25 IU/ml in all blood groups. Blood group O showed significantly lower VWF: Ag level than those of non-O blood group with P Ë‚ 0.01. The expression level of VWF: CB assay in the  blood groups were; A (0.784 ± 0.21 IU/ml); B (0.788 ± 0.16 IU/ml); O (0.630 ± 0.31 IU/ml); non-O (0.788 ± 0.19) and 0.720 ± 0.26 in all blood groups. Blood group O was significantly lower when compared with non-O blood group (p Ë‚ 0.0001). The mean ADAMTS-13 activities were as follows: A (113.9 ± 23.95%); B (113.5 ± 19.45%); O (131.6 ± 23.9%); non O (113.7 ± 21.79%) and 121.5 ± 24.40% in all blood groups. ADAMTS-13 activity was significantly higher in blood group O when compared with non-O (p Ë‚ 0.001). VWF: Ag level were higher compared to Caucasian values.

Keywords: Von Willebrand disease, ABO, von Willebrand factor,von Willebrand factor collagen binding and ADAMTS-13.