Rapid detection of alpha + thalassaemia deletion & alpha-globin gene triplication by Gap-PCR in Indian subjects.

BACKGROUND & OBJECTIVES: Southern blot hybridization is the commonly used method to delineate alpha globin gene defects. This technique is time consuming, requires a large amount of genomic DNA and radioactive probes for detecting the mutations, which limits its use in diagnosis. The present paper emphasizes the efficacy of a well-established Gap-PCR technique in the Indian set up to detect defects of the alpha globin gene in clinics and laboratories engaged in the diagnosis of thalassaemias. METHODS: A total of 190 normal subjects (voluntary blood donors), 183 individuals with heterozygous beta-thalassaemia and 19 with homozygous beta-thalassaemia were screened for -alpha 3.7, -alpha 4.2 deletions and for triplication of alpha gene (alpha alpha alpha anti 3.7). RESULTS: The use of normal and mutant primers in Gap-PCR revealed eight (4.2%) normal individuals, 22 (12%) individuals with heterozygous beta-thalassaemia and 1 (5.2%) with homozygous beta-thalassaemia as carriers of single- -alpha 3.7 deletion. Amplified fragment of 1.8 kb indicated the presence of alpha gene triplication (alpha alpha alpha anti 3.7) in 4 subjects with heterozygous beta-thalassaemia. Normal alpha-genotype (alpha alpha/alpha alpha) was found in 250 samples. However, none of the studied samples revealed the presence of -alpha 4.2 deletion. INTERPRETATION & CONCLUSION: Gap-PCR is a robust, simple, rapid and non-radioactive technique thus useful in diagnostic laboratories for the detection of common alpha-thalassaemia mutations.