On the Levels of Hemoglobins F and A2 in Sickle-cell Anemia and Some Related Disorders

Abstract

Results of analyses of Hb-A₂ and/or Hb-F levels in more than 300 Negro subjects with sickle-cell anemia, the two forms of Hb-S-β- thalassemia, Hb-S trait, Hb-SC disease, the Hb-S hereditary persistence of Hb-F (HPFH) condition, /3-thalassemia trait, and the HPFH heterozygosity are presented. Ages of the patients ranged from 1 to 70 years; several patients were studied repeatedly over long periods. Previously published data indicate that the levels of Hb-A2 and Hb-F in normal individuals range from 2.0 to 3.0% and from 0.2 to 1.0%, respectively. In subjects with a sickle-cell trait the level of Hb-A2 is slightly higher but the level of Hb-F does not differ from that of normal adults. Conclusions from recent observations are: (1) Sickle-cell anemia. The level of Hb-A2 is slightly higher than in normal adults and that of Hb-F ranges from 1 to 20%. No significant difference between the Hb-F levels of male and female patients of different ages has been noted. The level of Hb-F tends to remain constant in subjects 5 years old and older. (2) Hb-S-β-thalassemia. The level of Hb-A2 in either Hb-S-β⁺-Th or Hb-S-β°-Th is elevated to the same extent as in β-thalassemia heterozygotes. In a few cases a Hb-A2 level that did not differ from that seen in many Hb-S homozygotes was observed. The level of Hb-F in the two conditions does not differ from that observed in sickle-cell anemia. Definite diagnosis of Hb-S-β°-Th requires careful hematologic evaluation and family studies. The presence of small amounts of Hb-A aids in the diagnosis of the Hb-S-β⁺-Th condition. (3) Hb-S-HPFH. The level of Hb-A₂ is decreased and that of Hb-F usually above 20%. These observations, together with findings indicating minimal hematologic abnormalities and an equal distribution of Hb-F within the erythrocytes, make the diagnosis of this condition possible.