BENGALURU: A study using Next Generation Sequencing (NGS) to determine carrier frequency and to look out for any mutations in common genetic disorders in Indians, done by MedGenome Labs in Bengaluru, and Sir Ganga Ram Hospital, New Delhi, found that out of the 200 participants, 52 (26%) were found to be carriers of one or more rare genetic disorders, 12 individuals (6%) were identified to be carriers for congenital deafness, 9 individuals (4.5%) were carriers for cystic fibrosis and 2 individuals were detected to be carriers for the Pompe disease.
The study showed a higher carrier frequency for these disorders, which was contrary to the generally held view about their low prevalence in Asian Indians. “The disease causing variants observed for disorders such as deafness, cystic fibrosis, Pompe disease, Canavan disease, primary hyperoxaluria, junctional epidermolysis bullosa, galactosemia, medium chain acyl CoA deficiency etc. were different from what is seen in the Western population. Thus, this pilot study highlights the importance of having a Genetic Variant Database for the Indian population,” a press release said.
The 22-month study was done on a North Indian population, where 200 individuals were screened for pathogenic variants in shortlisted 88 genes, using NGS technology. These variants were classified as per the guidelines of American College of Medical Genetics. Dr Sunita Bijarnia-Mahay, author and senior consultant, Institute of Medical Genetics & Genomics, Sir Ganga Ram Hospital, said, “This study brought surprises by detecting those genetic disorders like cystic fibrosis which were not thought to be common.
In future, such NGS-based screening tests will benefit not only young couples planning a baby, but also healthcare officials in charting out prevention strategies for the Indian population.” Currently, there is no carrier screening programme available in India, except for limited screening for Thalassemia and Down’s Syndrome. Dr Sheetal Sharda, senior consultant, Clinical Genetics, said couples may not even be aware that they could be carrying a genetic variant.
In most cases, carriers of a genetic disorder are asymptomatic and may have no family history, and unfortunately, their carrier status is often confirmed only after an affected baby is born. Prof I C Verma, senior consultant and adviser, Institute of Medical Genetics & Genomics, Sir Ganga Ram Hospital, said those with IVF pregnancies, consanguineous couples (descendants with the same ancestor) and those with previous history of abnormal babies must get carrier testing done before their next pregnancy, to prevent the birth of babies with genetic disorders.