Objectives
Coexistence of α-thalassemia in sickle cell disease/trait is common. Furthermore hemoglobin A2 (HbA2) has been reported to be higher in sickle cell trait patients in combination with α-thalassemia.a Therefore we want to correlate the HbA2 percentages with the diagnosis of α-thalassemia with hemoglobin S (HbS) in our hospital.
Methods
We performed a retrospective analysis of the Multiplex Ligation-dependent Probe Amplification (MLPA) data between January 2014 and November 2018 of 165 patients, in the context of α-thalassemia. HbA2 % and HbS % were determined by capillary zone electrophoresis (CZE). Results of duplicates and patients with incomplete data were excluded. This resulted in a group of 119 patients of which 20 patients were hetero- or homozygous for HbS (2/20 patients ≤2 years were excluded). Pearson’s X2 was used to compare the HbA2 levels in patients with HbS with or without underlying α-thalassemia.
Results
Sixty-one percent (11/18) of the patients with HbS (3/7 homozygous for HbS; 8/11 heterozygous for HbS), had an underlying α-thalassemia. Four patients had a heterozygous α+-thalassemia (-α3.7/αα) and 7 had a homozygous α+-thalassemia. In patients with coexistence of HbS and α-thalassemia, statistically significant higher HbA2 levels (median HbA2 = 3.6%) (p= 0.02) were found compared to patients without underlying α-thalassemia (median HbA2 = 2.4%). The observed range of HbA2 was from 2.3-4.3% (2.3-3.8% for heterozygous and 3.1-4.3% for homozygous α+-thalassemia). Of the patients with heterozygous HbS and α-thalassemia, HbS was <35% in 7 cases (88%).
Conclusion
In our study population we found higher HbA2 levels in patients with a combination of HbS and underlying α-thalassemia. Therefore, we should think of the possibility of underlying α-thalassemia in HbS patients with increased HbA2. If this finding correlates with other hematological parameters (diminished hemoglobin and/or mean corpuscular volume/hemoglobin), molecular analysis might be useful.

Capillary zone electrophoresis measured HbA2 aiding in diagnosis of underlying a-thalassemia in the presence of HbS