Influence of Alpha Thalassaemia on Hematological and Clinical Presentations in Patients of Sickle Cell-β-Thalassaemia with IVS I-5 (G→C) Mutation (HBB: C.20A > T/HBB: C.92 + 5G > C).

Sickle cell-β-thalassaemia (Hb S/β-thal) results from the compound heterozygosity of sickle cell and β-thalassaemia alleles. The influence of α-globin genotypes on clinico-hematological and biochemical parameters in 404 cases of Hb S/β-thal with IVS I-5 (G→C) (HBB: c.20A > T/HBB: c0.92 + 5G > C) mutation was studied. Normal α-globin genotype (αα/αα), heterozygous α-thal (-α/αα) and homozygous α-thal (-α/-α) were found in 204 (50.5%), 114 (28.22%), and 86 (21.29%) cases respectively. The overall incidence of α-thal was found to be 49.5% and allele frequencies for α-3.7 and α-4.2 α-thal were found to be 0.23 and 0.11 respectively. RBC count, total hemoglobin and hematocrit levels were significantly higher in homozygous α-thal, intermediate in heterozygous α-thal and lower in normal α-globin genotype. Painful events per year, requirement of blood transfusion per year and hospitalization per year did not show any significant differences across these α-globin genotypes, although, the requirement of blood transfusion per year and hospitalization per year were more in patients with normal α-globin genotypes. Asymptomatic cases were higher in prevalence among homozygous α-thal (9.3%) compared to the other two groups. The age at clinical presentation was marginally later than that among other two groups. The present study shows quite high prevalence of α-thal trait among patients with Hb S/β-thal with IVS I-5 (G→C) mutation. Although influence of homozygous α-thal was found to have some protection further follow up and studies are needed to find its significance.