β-Thalassemia mutations in subjects with borderline HbA₂ values: a pilot study in North India.

BACKGROUND

Interpreting hemoglobin high performance liquid chromatograms with borderline HbA₂ values is often problematic, especially in antenatal cases if the partner is a known thalassemia trait.

METHODS

We tested for underlying β-thalassemia mutations in 25 subjects with borderline HbA₂ values (between 3.0%-4.0%). Amplification refractory mutation system (ARMS-PCR) was used to detect the five common Indian β-thalassemia mutations: (IVS-I-5 (G>C), IVS-I-1 (G>T), codons 8/9 (+G), codons 41/42 (-TTCT) and 619 bp deletion). β-Globin gene sequencing was performed if no mutation was detected.

RESULTS

A β-globin gene defect was identified in 8 (32%) of the 25 cases with HbA₂ 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 +1 (A>C) mutation on gene sequencing. IVS-I-1 (G>T) and codons 8/9 (+G) 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.