Determination of the Level of von Willebrand Factor, ADAMTS13, and Ratio of ADAMTS13:von Willebrand Factor in Sickle Cell Disease Patients.

Background: Sickle cell anemia (SCA) is a hypercoagulable state characterized by a significant alteration in hemostatic parameters which may predispose an increased risk of vaso-occlusive crisis (VOC). Sickle cell disease (SCD) is the most common genetic disorder in sub-Saharan Africa. Nigeria bears a high disease burden with an estimated prevalence of 1%-3% of its population being affected by the disease. The study seeks to determine the role of von Willebrand factor (VWF), ADAMTS13, and the ratio of ADAMTS13:VWF antigen in the pathogenesis of VOC.

Objective: The objective of this study is to evaluate the level of VWF, ADAMTS13, and their ratio in SCD subjects in Calabar and to determine their role in the pathogenesis of VOC.

Methodology: This is a comparative study carried out at the University of Calabar Teaching Hospital (UCTH), Calabar. Sixty SCA patients were evaluated in VOC and steady states as well as five parented healthy controls. VWF: Ag and ADAMTS13:Ag were evaluated using Assaypro enzyme-linked immunosorbent assay kits with Lot nos. 01751728 and 04222167R, respectively. Data were analyzed by IBM SPSS Chicago software version 21. The study was approved by the UCTH Institution Ethical Review Board.

Results: The mean ages of the SCA subjects and controls were 23.5 ± 7.2 years and 26.5 ± 5.6 years, respectively (P = 0.706). There were 23 (38.3%) males in the SCA group and 21 (42.0%) females in the controls. There was no significant difference in their sex distribution (P = 0.063). The mean (standard deviation [SD]) of VWF in VOC, steady state, and controls were 2.52 ± 0.34, 1.34 ± 0.23, and 1.41 ± 0.23 IU/mL, respectively. The differences in mean were significantly higher in VOC state (P = 0.003). The mean ± SD of ADAMTS13 in VOC, steady state, and controls were 0.61 ± 0.10, 0.44 ± 0.06, and 0.62 ± 0.10 μg/L, respectively. ADAMTS13 levels did not differ significantly across the groups (P = 0.270). Similarly, there was no significant difference between ADAMTS13:VWF ratios across the groups (P = 0.318).

Conclusion: VWF level is elevated in VOC state and thus may be implicated in the pathogenesis of VOC. ADAMTS13 and the ratio of ADAMTS13:VWF are not significantly affected in VOC.