Sample: Whole Blood 0.5 mL
Schedule: Twice weekly
Range: HbA2 levels < 3.5% of total Hb
Remarks: Hemoglobin A2 levels have special application to the diagnosis of beta-thalassemia trait, which may be present even though peripheral blood smear is normal. The microcytosis and other morphologic changes of beta-thalassemia trait must be differentiated from iron deficiency. Low MCV may include the majority of beta-thalassemia trait patients but does not differentiate iron-deficient individuals.
Low Hb A2 levels occur in untreated iron deficiency. If the beta-thalassemia is associated with iron deficiency, the Hb A2 level falls, making the differentiation even more difficult (corrected after iron therapy).1 The most definitive evidence for presence of beta-thalassemia trait is genetic (family study). Offspring of a person with thalassemia major will have beta-thalassemia trait. Hb A2 may be increased in megaloblastic anemia and may be decreased in sideroblastic anemia, Hb H disease, and erythroleukeia.