Filter-based kits developed for TB diagnosis, drug-resistanc
To address the TB diagnostic challenges, a multi-institutional team has developed three cost-effective kits that improve the sensitivity of smear microscopy, enable transport of sputum samples at ambient temperature without using bio-safe containers, and extract DNA for diagnosing drug-resistant TB. The three kits are — TB Detect, TB Concentration & Transport, and TB DNA Extraction.

The TB Detect kit is for diagnosis using LED fluorescence microscopy, while the TB Concentration & Transport, and the TB DNA Extraction kits together are for detection of drug-resistance. The TB Detect kit helps increase the positivity of LED fluorescence microscopy by about 5%, while the TB DNA Extraction kit allows the detection of drug-resistant TB bacteria with a high level of sensitivity. The results of the study were published in PLOS ONE.

The TB Detect kit currently costs Rs.100 per sample, Rs.100 for the TB transport kit and Rs.85 for the DNA extraction kit.

In the case of the TB Detect kit, the team led by Prof. Jaya Sivaswami Tyagi from the Department of Biotechnology at AIIMS used a simple filter-based system to separate TB bacteria from the sputum to improve the sensitivity of LED fluorescence microscopy. In this, the sputum, which is viscous, is first liquefied using a proprietary reagent and pre-filtered. The bacteria in the liquefied sputum pass through a paper-like filter while some of the cell debris are retained on the filter.

The liquefied sputum containing the TB bacteria then comes in contact with a highly porous, plastic membrane filter underlain by multiple fibrous pads kept at the base of the filter device. While the sputum gets sucked by the fibrous pad due to capillary forces, the bacteria remain on the membrane.

The kit for TB diagnosis was tested at the TB Hospital, Ambala and the National Institute of Tuberculosis and Respiratory Diseases (NITRD), Delhi using 1,190 samples. The kit for diagnosing drug-resistance was tested on 148 samples at NITRD and Translational Health Science and Technology Institute (THSTI).