B-Thalassemia mutations in subjects with borderline HbA ₂ values: A pilot study in North India

Background: Interpreting hemoglobin high performance liquid chromatograms with borderline HbA ₂ values is often problematic, especially in antenatal cases if the partner is a known thalassemia trait. Methods: We tested for underlying βthalassemia mutations in 25 subjects with borderline HbA ₂ values (between 3.0%-4.0%). Amplification refractory mutation system (ARMS-PCR) was used to detect the five common Indian βthalassemia mutations: (IVS-I-5 (G>C), IVS-I-1 (G>T), codons 8/9 (qG>, codons 41/42 (-TTCT) and 619 bp deletion). βGlobin gene sequencing was performed if no mutation was detected. Results: A βglobin gene defect was identified in 8 (32%) of the 25 cases with HbA ₂ levels ranging from 3.5%-3.9%. ARMS-PCR revealed IVS-I-5 (G>C) in three, 619 bp deletion in two and codons 41/42 (-TTCT) in one case. Two cases had CAP q1 (A)C) mutation on gene sequencing. IVS-I-1 (G>T) and codons 8/9 (qG> were not found in this small cohort. Conclusions: Mutation analysis should be offered to all at-risk couples with borderline HbA2, especially those with values between 3.5% and 4.0% and microcytic hypochromic indices. Significant mutations different from those in other ethnic populations were seen in this small institution-based study.