The much awaited national drug resistant survey is likely to conclude by next month. The survey which involved doing genotyping studies from TB strains collected from across the country will offer clinical data on molecular epidemiology of TB in the country.

Currently 5000 samples have been collected from patients across the country to determine sensitivity of 13 anti-TB drugs and 80 per cent drug susceptibility testing (DST) process has been accomplished.

The survey is very significant as in addition to diagnosing TB, there is also a need to test for drug resistance so that the most effective TB treatment can be provided.

The universal drug susceptibility testing (DST) is part of the World Health Organisation's strategy to end TB by 2035.

Culture is currently the main tool for drug susceptibility testing (DST). However, not only is the length of time it takes is a problem, but it also requires trained personnel and expensive laboratory equipment.

Advanced diagnostic tool like Genexpert has gained further impetus as experts advocate the need for DST to be made available to all patients and then provide individualised treatment with the help of DST. Now there is also a thrust upon designing treatment regimens to offer optimal and shorter dosages for children suffering from TB.

Genexpert test is a molecular test which detects the DNA in TB bacteria. It uses a sputum sample and can give a result in less than 2 hours. It can also detect the genetic mutations associated with resistance to the drug rifampicin. New TB tests are required because of the difficulties associated with the tests that are currently used both to diagnose TB as well as to detect drug resistance.

Traditionally TB has been diagnosed by looking for evidence of TB bacteria either through the use of the chest X-ray, through sputum smear microscopy, or through the culturing of bacteria. Each of these TB tests has their disadvantages, one of the most significant for culture being the time that it takes and for sputum in terms of accuracy.

Currently, a patient is first tested for simple TB that needs six to nine months of treatment. If the patient doesn't respond to this treatment within three months, he is tested further for drug resistance. If the patient is resistant to two of the normal drug regimens, he is said to suffer from multi-drug resistant (MDR) TB. If the patient is resistant to more than two drugs as well as an antibiotic injection given to MDR-TB patients, he has extensively drug-resistant (XDR) TB.

Drug-resistant TB needs over two years of treatment, with drugs costing more than Rs.2 lakh.

India has the highest tuberculosis burden in the world, accounting for nearly one-fourth of the global incidence. Experts advocate that there was a need to have epidemiological data on TB through a nationwide surveillance as was done in China a few years ago.

As of today 19 million TB patients have been treated and 3.5 million additional lives saved as a part of Revised National Tuberculosis Control Programme (RNTCP).