ICMR's top research institute developing sputum-free tests for diagnosing TB

Chennai : ICMR's top tuberculosis research institute NIRT is in the process of developing and validating sputum-free tests using blood, stool, urine and saliva samples for diagnosing the disease.

Sputum is a thick mucus found in the respiratory tract, typically as a result of infection.

The Director of ICMR's National Institute for Research in Tuberculosis (NIRT), Dr Padmapriyadarsini C, said accurate, fast non-sputum-based tests for the detection of tuberculosis are urgently needed to close the diagnostic gap.

"In conditions where you do not have sputum for tests such as in children, elderly, or in the case of extra-pulmonary TB where sputum is not very helpful, any other sample -- stool, urine, blood or saliva may be used for diagnosing TB," she told PTI.

In small children obtaining sputum specimens for testing is particularly difficult. With them being least likely to be diagnosed, they are most at risk of severe disease, Dr Padmapriyadarsini said.

Tuberculosis is diagnosed by detecting the bacteria in the sputum. But in blood-based biomarker discovery scientists are looking at how the TB bacteria affects the host's immune system, Dr Subash Babu, an NIH scientist and Scientific Director of ICER-India told PTI. The ICER in collaboration with NIRT is doing the research in this matter.

"We are in the process of developing blood-based biomarkers that will provide the basis for accurate diagnostic tests for TB in children and predict treatment outcome," Dr Babu said.

In adults, blood-based biomarkers may be also useful for identifying those at risk of TB treatment failure or recurrence of the disease, he said.

Blood biomarkers may help detect extra-pulmonary tuberculosis which affects other parts of the body such as lymph nodes, bones, brain or kidneys.

"We have published a number of research articles in high-quality scientific journals about the identification of host molecules which can aid in the diagnosis of pulmonary and extra-pulmonary TB in children and adults, as well as for predicting treatment failure or recurrence in adults before they begin anti-TB treatment," Dr Babu said.

It is estimated that of the total tuberculosis patients in India, around 6 per cent are children. Diagnosing TB among the paediatric population is a challenge due to low bacterial load and the inability of children to expectorate sputum.

Also, there are no practical gold standard tests for the detection of TB in children Dr Siva Kumar, a Senior Scientist at NIRT said.

"Most children are missed in diagnosis because of these challenges. Presently, gastric juice is the choice of sample for the detection of TB in the paediatric population. This process is also difficult as it involves inserting a tube into the stomach for collecting gastric juice," Dr Kumar said.

"Usually, paediatric patients swallow their sputum and this comes out through the stool. Thus stool testing can be used for detection of pulmonary tuberculosis," he said.

To close the diagnostic gap, he said NIRT has developed a methodology for the extraction of DNA from stool samples for the diagnosis of tuberculosis in paediatric patients.

Now, this method is under validation in the laboratory and will undergo multicentric studies before being used in the field, Dr Kumar added.