The development of haemoglobin A2 in normal negro infants and in sickle cell disease.

The development of haemoglobin A2 levels from birth to 3 years has been compared in normal, beta-thalassaemia trait, sickle cell (SS) disease, and S-beta-thalassaemia genotypes. Hb A2 levels were almost identical in normals and in children with SS disease at 1, 2 and 3 years. The most rapid increases in Hb A2 levels occurred before 6 months but levels were still rising at the end of the third year. Sickle cell-beta+ thalassaemia could be differentiated from SS disease by the higher Hb A2 levels between 6 months and 1 year. Insufficient data were available on S-beta o thalassaemia but since Hb A2 levels in this condition are generally higher than those in S-beta+ thalassaemia, differentiation from SS disease may may also be possible from the age of 6 months.