Doctor modifies TB test for rural areas, makes it cost-effec
Due to intermittent supply of electricity in rural areas, diagnosis for extrapulmonary tuberculosis cannot be established easily. Also, most of the existing tests are costly and require sophisticated set up and skillful manpower.

Prof Kusum Sharma from the PGI department of microbiology has modified a diagnostic tool for extrapulmonary tuberculosis (EPTB), known as loop-mediated isothermal amplification (LAMP) test, that can be carried out without electricity in villages and low resource centres, at a very low cost.

Although the diagnostic technique exists already, Prof Sharma has customised it and made it more sensitive and specific for TB diagnosis. The diagnostic tool is an Isothermal nucleic acid amplification technique (NAAT) used for other infections, viruses and even TB.

So, what is unique about this modified technique? “Our innovation is in using two different types of genes together for TB diagnosis. If the part of the DNA of TB bug is missed by one gene, the same can be picked up by the other gene. Therefore, it increases the sensitivity and specificity of the test,” said Prof Sharma.

Moreover, other molecular diagnostic tests like polymerase chain reaction (PCR) need costly equipment, while this modified test only uses a simple temperature-regulated water bath. This technique, in comparison to PCR, needs minimal training and can even be carried out by any literate person with simple training and instructions on how to conduct the test.

Compared to the existing molecular tests, this tool takes 90 minutes to diagnose TB and it takes 6-7 hours for a diagnosis by using the PCR test techniques.

How does the technique work? It needs patients’ sample from where the DNA is extracted. To detect the presence of the TB DNA in this sample, some reagents are added and for an hour the tubes are placed in a hot water tub. When a dye is added to the tubes, colour changes to yellow and this confirms presence of TB DNA in the sample.

“So, all it needs is a water bath which may or even be a battery-operated tub. The cost is less than Rs 100, while the PCR test costs Rs 500-600 and takes 6-7 hours for a confirmed diagnosis,” said Prof Sharma.

“We do smear test, culture and do couple of molecular tests. However, as TB meningitis is an emergency and needs rapid and early diagnostics, this test is handy,” she added. Developing this modification took 4-5 work years and is ongoing. “The work is at the stage of evaluation and has been tested on patients. We have evaluated on various samples of more than 500 patients suffering with ocular (eye) TB, TB of the joints and TB meningitis etc,” said Prof Sharma.

India accounts for one fourth-of the world’s estimated 10.4 million new TB cases per year and nearly a third of the 1.7 million annual TB deaths. Although extrapulmonary TB accounts for 15-20% of the pulmonary TB, for a country like India, these numbers are quite significant.

Dr. P●●●●m D●b and 81 others like this36 shares