Beta Thalassemia Carrier Detection in Individuals with Borderline Normal Hemoglobin A 2 Levels

Transfusion-dependent β-thalassemia is a significant public health challenge in many countries. Prevention through carrier detection enables counseling for at-risk couples and informed decision-making. Beta-thalassemia carriers are identified by elevated hemoglobin A2 levels (≥3.6%). However, individuals with borderline HbA2 levels of 3.0-3.5% fall within a diagnostic gray zone. Identifying carriers in this group is crucial given the significant medical, financial, and psychosocial implications. Therefore, this study aimed to identify β-thalassemia carriers among individuals with borderline hemoglobin A2 levels to enhance early detection and provide accurate clinical guidance for this population. Samples received for thalassemia screening by HPLC at Aga Khan University Clinical Laboratories were assessed. Those with HbA2 levels of 3.0-3.5% were included, excluding individuals with iron deficiency. Informed consent was obtained for β-globin gene sequencing. HbA2 was measured by HPLC, and pathogenic mutations identified by DNA sequencing were correlated with phenotype using the Hemoglobin Variant Database. Data were analyzed using SPSS. From July 2022 to December 2024, 85 individuals with borderline HbA2 levels were identified. After excluding those with iron deficiency, 55 participants (median age 24 years; 54.5% female) were included in the analysis. Heterozygous β-globin mutations were detected in 6 cases (10.9%), most commonly CAP + 1 (A > C). No significant hematological differences were observed between mutation-positive and mutation-negative groups, and no mutations were found in individuals with HbA2 <3.2%. In our study, β-thalassemia trait mutations were detected in 10.9% of subjects with borderline HbA2 levels, underscoring the need to investigate such cases at the molecular level to avoid missing individuals at risk.