Hemoglobin A2 and F, Blood Clinical Information Discusses
physiology, pathophysiology, and general clinical aspects, as
they relate to a laboratory test Hemoglobin F (Hgb F), composed
of 2 alpha and 2 gamma globin chains, is the normal hemoglobin
of the fetus and newborn. Normally in the second trimester,
gamma chain production (and Hgb F levels) decrease and beta
chain production increases, resulting in increasing levels of
Hgb A, the major normal adult Hgb (2 alpha and 2 beta globin
chains). Hgb A2 (2 alpha and 2 delta globin chains) also
comprises a small amount (<3.3%) of Hgb normally found in
adults. Hgb A2 values at birth are <1%. Assisting in the
diagnosis of beta-thalassemia Quantitating the percent of
hemoglobin F (Hgb F) present Assisting in the diagnosis of
disorders with elevated levels of Hgb F Hemoglobin A2 (Hgb A2)
values of 3.5% to 9% are found in beta-thalassemia trait. In
beta-thalassemia major, hemoglobin F (Hgb F) may be 30% to 90%
or even more of the total hemoglobin. Hgb F concentration