The level of Hb F-Sardinia (alpha 2A gamma 2(75)Ile----Thr) in the fetal hemoglobin of Sardinian beta-thalassemic homozygotes determined by isoelectric focusing.

A simple thin-layer isoelectric focusing technique was used to separate Hb F-Sardinia, containing the A gamma T-globin chain, from the Hb F containing the G gamma- and the A gamma I-globin chains. The identity of the slow-moving Hb F fraction as Hb F-Sardinia was verified by PAGE. A negative correlation (R2 = 0.747, p less than 0.001) was found between the percent Hb F-Sardinia and percent G gamma-chain in homozygotes for beta-thalassemia. Of 31 Sardinian beta-thalassemic patients studied, 21 were homozygous and eight heterozygous for the A gamma T polymorphism with a gene frequency of 0.823. The mean values of Hb F-Sardinia were 39.1 +/- 5.9% for the homozygotes and 17.1 +/- 3.6% for the heterozygotes. The percentage of Hb F-Sardinia found in beta o-thalassemic newborns was similar to that of corresponding normal newborns who also had the A gamma T polymorphism. No measurable differences in the percent Hb F-Sardinia level were observed among beta o-thal patients who were polytransfused, beta o-thal patients studied before transfusion, and beta o-thal patients exhibiting the intermediate form of the disease who had never been transfused.