- Hemoglobin A → α2Β2
- Hemoglobin A2 → α2δ2
- Fetal hemoglobin → α2γ2
Hemoglobin A2 it is found in minimal quantities in fetal erythrocytes, but its fraction increases after birth reaching values of 2-3% in children and adults. Normally, in the red blood cells of a healthy adult we find three different types of hemoglobin, which differ from each other in genetic synthesis and composition of globin chains:
The α chains are made up of 141 amino acids and are identical for the three different hemoglobins
Hemoglobin A levels2 they reach the percentage values typical of adult life only after the 6th – 12th month of life.
- Hemoglobin values considered normal in healthy individuals over 12 months of age are between 2.0% and 3.2%.
Causes of Hemoglobin A2 high
In children and adults, hemoglobin A values2 may increase in the presence of:
* Increased hemoglobin A2 it is one of the most typical markers of the carrier of Β-thalassemia genes. In this context, the measurement of hemoglobin A2 (HbA2) in the blood plays a key role in Β-thalassemia screening programs, to quantify the risk that the couple’s offspring will be affected by Beta thalassemia, a high risk if both parents are carriers of the genetic defect, highlighted by HbA percentages2 higher than the norm. Unfortunately, in some cases HbA levels2 are unchanged despite the subject being a carrier of Β-thalassemia genes (for example in the case of the simultaneous presence of a severe iron deficiency); furthermore, the difference in HbA values2 among healthy subjects and carriers of the thalassemia trait it is small. For this reason, analytical measurements must be particularly accurate and the results interpreted together with those of other haematological investigations.
Causes of Hemoglobin A2 Low
Hemoglobin A2 values may decrease in the presence of: