Sickle Cell Disease Screening in Northern Nigeria: The Co-Existence of Β-Thalassemia Inheritance

Abstract

Background: Despite the high burden of Sickle Cell Disease (SCD) in Nigeria, the underlying haemoglobinopathy profile remains uncertain. Although a number of urbanised areas have pilot hospital-based newborn screening programmes, the impact of the disease in rural areas is unknown.Methods: From January 2010 to December 2011 this community-based study screened children aged 0-60 months in 29 randomly selected local communities of three adjoining northern Nigerian states - Abuja, Kaduna and Katsina. For infants 0-6 months, blood spots were used and for infants 7-60 months EDTA blood samples were analysed using high performance liquid chromatography (HPLC). 31 selected sample with high Hb A2 (3.5-7.4%) were further analysed using molecular diagnosis to ascertain the presence of the Beta Thalassemia gene.Findings of 10,001 infants and children screened, 269 (2.69%) had a SCD diagnosis; 90% of which were HbSS (n=243), 5% HbSC (n=13), 3% with high A2 > 6% (possible S with existence β thalassaemia (n=9) and 1% HbSD (n=2). 74% of infants screened were HbAA (n=7,391). 2,341 (23%) were carriers; 96% HbAS (n=2,236), 2% HbAC (n=51), 1% HbAD (n=25) and 1% HbABeta-thal (n=22). HbSβo was confirmed by molecular analysis from the 31 selected samples.Conclusion: Early infant diagnosis of SCD in Northern reports an incidence of 1.72%, Homozygous SS accounts for over 90% of cases; double heterozygous SC is very low (4%). The presence of beta (β) thalassemia coinheritance is now confirmed using molecular analysis. Community and family counselling and educational material in Northern Nigeria must include the risk of beta thalasemia inheritance.