Factors Influencing Hb A₂ Interpretation and Testing Recommendations

Conditions That Can Lower Hb A₂ in True Carriers

• Iron deficiency can mask the elevated Hb A₂ that is typical of beta‑thalassemia carriers, leading to falsely low Hb A₂ values. The British Society of Gastroenterology reports this effect in multiple studies. 1
• Co‑inheritance of alpha‑thalassemia may reduce Hb A₂ concentrations below the usual carrier range, potentially obscuring a diagnosis of beta‑thalassemia trait. 2
• Co‑inheritance of delta‑thalassemia decreases Hb A₂ production, also resulting in lower measured Hb A₂ levels. 3

When to Re‑evaluate Hb A₂ Testing

• In individuals with microcytosis but normal iron studies, Hb electrophoresis should be repeated after iron repletion to avoid missing a carrier state masked by iron deficiency. 1

Guideline Recommendations (British Society of Gastroenterology)

• The British Society of Gastroenterology advises that Hb electrophoresis be performed in patients who exhibit microcytosis with normal iron parameters, especially when the patient belongs to an ethnic group at higher risk for thalassemia. 1

Interpretation Checklist Before Excluding Thalassemia Trait

• Verify the presence of microcytosis (mean corpuscular volume reduced disproportionately to any anemia) and confirm normal iron status prior to definitively ruling out beta‑thalassemia trait. This approach is endorsed by the British Society of Gastroenterology. 4