Developmental changes in hemoglobin F levels during the first two years of life in normal and heterozygous beta-thalassemia infants.

To study the developmental pattern of hemoglobin F (HbF) during the first two years of life, levels of HbF were estimated in two groups of infants: 117 normal infants and 98 heterozygotes for beta-thalassemia, all aged between 1 and 24 months. The results may be summarized as follows: (1) Levels of HbF in beta-thalassemia heterozygotes were significantly higher than those of normal infants of the same age (P less than .01). (2) A reference curve for the decline of HbF in infants with beta-thalassemia trait was established to facilitate the diagnosis of heterozygotes during this period of life. (3) Hemoglobin A2 (HbA2) was also higher in beta-thalassemia heterozygotes than in normal infants of the same age. HbA2 increases with increasing age, reaching normal adult values at age 5 to 6 months. It is postulated that the higher level of HbF in heterozygous infants during the first two years of life is associated with the presence of the beta-thalassemia gene, which influences the increased synthesis of HbF in red cell.