Hb Bart's and its significance in the South African Negro.

The haematological indices of cord bloods from 430 South African Negro babies were determined by electronic cell counting and their haemoglobin (Hb) patterns examined by alkaline cellulose acetate electrophoresis. A fast-moving, anodal band, identified as Hb Bart's, was found in 7 (1,6%) of the specimens, this being the lowest incidence of the variant yet found in an indigenous African population. The levels of Hb Bart's ranged from 1.3 to 5.5% of the haemoglobin. These findings were confirmed by alkaline-starch gel electrophoresis and at the same time absence of the slow-moving haemoglobin, Hb Constant Spring was established. Subsequent follow-up of 4 of the infants at 4 months of postnatal life showed that the abnormal component had disappeared. The babies with Hb Bart's had a marked microcytosis and low mean corpuscular haemoglobin levels whilst their parents showed no haematological or electrophoretic signs of alpha-thalassaemia. The significance of these findings is discussed in the light of previously reported studies on various Negro groups.