Version July 2025
| Reduced Hb A2 | Increased Hb A2 | ||
| Condition | Comments | Condition | Comments |
| Alpha thalassemia | Reduction correlates with severity of thalassemia | Sickle cell disease | Artifact of some HPLC systems |
| Alpha globin gene variants | Hybrid Hb A2 might not separate | Beta thalassemia | Typically 4 to 6%; rarely up to 10% with 5' HBB gene deletions |
| Delta globin gene variants | Variant can be poorly expressed | Sickle cell-beta thalassemia | >3.5%; may be artifact of some HPLC systems |
| Delta-beta thalassemia | Half normal in heterozygotes | Sickle cell disease with alpha thalassemia | Typically 4 to 5%; due to a post-translational effect |
| Delta thalassemia | Usually approximately half normal | Sickle cell trait | Artifact of some HPLC systems |
| Gene deletional HPFH | Half normal in heterozygotes | Unstable hemoglobins | |
| Hb Lepore | Half normal in heterozygotes | Megaloblastic anemia | Modest increases |
| Sideroblastic anemia | Due to impaired alpha globin synthesis | Hereditary spherocytosis | Not uniformly elevated |
| Iron deficiency | Reduction correlates with severity of iron deficiency | KLF1 gene mutations | Lower than in beta thalassemia |
| Acute myeloid leukemia | Minor reduction | Congenital dyserythropoietic anemia, type 1 | Lower than in beta thalassemia |
| Myelodysplastic syndrome | Only reduced in a minority of cases | Hyperthyroidism | Lower than in beta thalassemia |
| Juvenile chronic granulocytic leukemia | Only reduced in a minority of cases with increased Hb F | Zidovudine treatment for HIV infection | Lower than in beta thalassemia |
