Prevalence and molecular basis of α thalassaemia in British South Asians

Abstract

Objectives To determine the prevalence and molecular basis of α thalassaemia in the British South Asian population, and the implications for genetic screening for haemoglobin disorders. Methods 397 South Asian subjects were screened for haemoglobinopathy with measurement of full blood count, haemoglobin electrophoresis, haemoglobin A2 quantification, and plasma ferritin determination. α Globin gene mapping was successfully performed on 266 stored buffy coat samples using a Southern blot technique after hybridisation with BglII and BamHI. Results Of the 266 subjects in whom gene mapping was performed, 28 had a single α+ thalassaemia deletion and one was homozygous for this deletion (gene frequency 0.056). Half of the heterozygotes had normal mean cell haemoglobin (MCH) values. A further 16 subjects had probable non-deletional α+ thalassaemia. None had α0 thalassaemia. Conclusions α Thalassaemia is by far the commonest haemoglobinopathy in British South Asian subjects, but is not a cause of serious genetic risk. Screening and counselling should focus on subjects with more marked red cell hypochromia (MCH <25 pg), thus concentrating resources on subjects of different ethnic origins who may carry the α0 thalassaemia gene.