Clinical Information

Fetal hemoglobin concentration is usually between 5% to 15% of the total hemoglobin in the high F or delta/beta-type of thalassemia minor. In beta-thalassemia major, fetal hemoglobin may be 30% to 90% or even more of the total hemoglobin.

Slight increases in hemoglobin F concentration are found in a variety of unrelated hematologic disorders, such as aplastic anemia, hereditary spherocytosis, and myeloproliferative disorders. In homozygous sickle cell disease, hemoglobin F concentration is often slightly increased.

Higher concentrations of hemoglobin F occur in hemoglobin S/beta O-thalassemia, in patients who are doubly heterozygous for the hemoglobin S gene, and in patients who have a gene for hereditary persistence of fetal hemoglobin (HPFH). These disorders may be differentiated by family studies or by flow cytometry studies for fetal hemoglobin, which reveals uniform intraerythrocytic distribution of hemoglobin F in HPFH and nonuniform distribution in hemoglobin S/beta-thalassemia. The electrophoretic finding of small quantities of hemoglobin A in a patient who has mostly hemoglobin S and a moderate increase in hemoglobin F is strong evidence of hemoglobin S/beta zero thalassemia (if the patient has not had a transfusion).