Micro-mapping of common α+ thalassaemia deletions (3.7 kb, 4.2 kb) in Sri Lanka and assessment of the contribution of α thalassaemia to hypochromic microcytosis

Abstract

Alpha thalassaemia is one of the most common haemoglobinopathies, but the exact prevalence and distribution of α thalassaemia in Sri Lanka is not well known. This study was an attempt to micro-map the distribution of the common α thalassaemia deletions in Sri Lanka and to assess its contribution to hypochromic microcytosis in the community. A national survey on haemoglobin disorders was carried out between 2009 and 2010, covering all 25 districts. A total of 7539 school children, 300 from each district were screened for haemoglobin disorders and anaemia. 3.7 kb and 4.2 kb common α+ deletional forms were analysed using PCR in 2038 individuals with hypochromic microcytic anaemia and 1305 individuals with non-anaemia individuals, representing all districts. The overall prevalence of α-thalassaemia was 9.5%, and 3.7 kb was the commonest deletion (8.3%) while the 4.2 kb deletion accounted for 1.2%. The prevalence of α-thalassaemia showed a remarkable variability within districts, ranging from 16.3% in Kurunegala to 3.0% in Galle. Contrary to common belief, it was found that α-thalassaemia due to single gene deletions was almost always associated with hypochromic microcytic anaemia.