CHENNAI: It is harder for natives of Tamil Nadu to find a matching donor for a stem cell transplant compared to other states in the country. The suspected villain: Their genes.

A study published recently in British medical journal 'The Lancet' found that the likelihood of finding a matching stem cell donor for patients with blood-related problems in Tamil Nadu is 44.2% provided the registry had 10 lakh donors. The situation is the opposite in Haryana, with people in that state having the best chances (81.2%) of finding a donor.

Experts say consanguineous marriages are to blame. Consanguineous marriages increase the chances of patients finding a match within their small community but limit the possibility of finding one from a general donor pool.

"Unlike in other countries, stem cell variation in India is complex and dependent on ethnic variation," said Dr Dolly Daniel, professor of the department of transfusion medicine at Christian Medical College, Vellore, who was party of the study team. "Our aim was to find the size and genetic composition of each region and its impact on the proportion of patients who will be able to ?nd a suitable match."

She said Tamil Nadu could be at the tail-end of the list of states they surveyed because of inbreeding and a limited number of donors.

Stem cells are used to regenerate and repair diseased or damaged tissues. Adult stem cells are drawn from bone marrow, blood and the umbilical cord and are used to treat blood-related ailments like leukemia, thalassemia and as well as immunodeficiency.

The possibility of finding a matching stem cell donor within the family is around 30%.

"Finding a matching stem cell donor for the remaining 70% is a complex process. Most seek a graft from registries of unrelated adult donors or banked umbilical cord blood units," said Dr P Srinivasan, co-founder and chairman of Jeevan Stem Cell Bank.

Although the India stem cell industry is estimated to touch $540 million (Rs 3,250 crore) by 2015, the study noted that in terms of the number of donors, India has lagged in meeting demand. The study surveyed 10 adult donor and umbilical cord bank registries and clinical transplant centres in India and studied stem cells of 26 239 individuals.

The possibility of finding a perfect match within India is an average of 14.4% for a registry size of 25,000 and touches 60.6% for a size of 10 lakh. Registries in the country currently have around 1 lakh donors. The study said only when Indian registries have more than 2 lakh donors would patients have a good chance of finding the right match.

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Toughest for Tamil Nadu patients to get donor stem cells