Published online by Cambridge University Press: 14 April 2020
common haemoglobinopathy, affecting 283 000 infants born annually. Sickle cell carriers are found throughout sub-Saharan Africa, the Mediterranean, the Middle East and the Indian subcontinent. Estimated frequency for sickle cell trait (HbAS) varies by ethnicity: 1:10 for African-Carribeans, 1:4 for West Africans, 1:100 for Cypriots and 1:100 for Pakistani, Indian. Haemoglobin S is created by the substitution of valine for glutamic acid (CAG → GTG), in the β-globin gene at position 6.