Hemoglobin A₂ levels in health and various hematologic disorders

Using a method involving elution of hemoglobin bands from cellulose acetate strips following electrophoresis of hemolysates, hemoglobin A₂ (Hb A₂) was quantitated in bloods from 300 healthy individuals and 904 patients. The percentage of Hb A₂ was elevated in β thalassemia heterozygotes and some patients who had megaloblastic anemia. In the latter, the highest Hb A₂ levels were observed in patients with the most severe anemia. Low Hb A₂ percentages were found in iron deficiency anemia, hereditary persistance of fetal hemoglobin, and Hb H disease. In iron deficiency anemia, the lowest levels of Hb A₂ were observed in association with the most severe anemia. Iron and folate deficiency each suppressed Hb A₂ levels in β thalassemia heterozygotes; however, vitamin B₁₂ deficiency did not alter the percentage of Hb A₂ in thalassemia. Malignant tumors, renal and hepatic insufficiency, chronic infections and inflammation, hemolytic disease, lead poisoning, aplastic anemia, leukemia, myelofibrosis, and hypothyroidism did not change Hb A₂ levels. The pathogenesis of altered Hb A₂ levels and their clinical significance in various diseases are discussed.