Prevalence of double heterozygotes of HbE and α-thal 1 (SEA) type in pregnancies and their partners that received antenatal care at Chiangrai Prachanukroh Hospital and reevaluated the cut-offs for differentiation.

Background: In Thailand, double heterozygotes of HbE and α-thal 1 (SEA) type is common. If pregnant women carrying this genotype conceive with partners who also carry the same genotype or who are carriers of α-thalassemia 1 (SEA) type, there is 25% chance of a fetus having Hb Bart's hydrops fetalis. This research aims to determine the prevalence of double SEA/E, compare the hematological parameters and HbE levels between pure HbE heterozygote and double SEA/E and reevaluate the cut-offs used to screen individuals with these genotypes.

Methods: In a retrospective study, 397 samples from individuals (partners who visited the Antenatal Care Clinic, Chiangrai Prachanukroh Hospital, Chiangrai Province, from 2017-2021) with HbE (hemoglobin typing EA) were collected. The samples were then classified as HbE with or without α-thalassemia 1 (SEA) type and RBC, Hb, Hct, MCV, MCH, MCHC, RDW and HbE level were compared between pure HbE heterozygote and double SEA/E via Student's t-test, with a p-value of 0.05. Cut-offs were reevaluated in samples that avoided interfering with iron-deficiency anemia via the parameters of sensitivity, specificity, PPV, NPV and accuracy.

Results: The study revealed that the prevalence of double heterozygotes of HbE and α-thal 1 (SEA) type was 12.6%. HbE level, MCV, MCH and MCHC in double heterozygotes of HbE and α-thal 1 (SEA) type were significantly lower, whereas RBC and RDW were greater (p < 0.001). Reevaluation for cut-offs revealed that, in the group with Hb < 10.0 g/dL, combined cut-offs (MCH + HbE level) and (MCV + MCH + HbE level) for the group with Hb = 10.0-11.9 g/dL were most effective, while a single cut-off (HbE level) was most effective for the group with Hb ≥ 12.0 g/dL.

Conclusions: Double SEA/E were also common among pregnant women and their partners who visited Chiangrai Prachanukroh Hospital, Chiangrai, Thailand. Using appropriate cut-offs for hematological parameters and HbE levels allows pure HbE heterozygote to be distinguished from double SEA/E.