Hemoglobin F and hemoglobin E/beta-thalassemia

Hemoglobin (Hb) F levels are high and variable in Hb E/beta -thalassemia, r anging from 10% to 80%. The high levels are secondary to expansion of the e rythron with ineffective erythropoiesis and selection in favor of cells abl e to make more gamma -globin. The variability in levels reflects the comple x processes involved in Hb F production. Important determinants include age , alpha -thalassemia, and genetic determinants of gamma -chain synthesis. O verall, percentage of Hb F correlates with total hemoglobin levels and decr eases steadily with age, alpha -thalassemia is associated with a lower perc entage of Hb F levels but a higher total hemoglobin level in Hb E/beta -tha lassemia.