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PGI doctor makes easy TB test available for rural India

PGI doctor makes easy TB test available for rural India

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. Most common presentation of neurotuberculosis in the Indian subcontinent is tuberculous meningitis (TBM). Early and rapid diagnosis is crucial for successful disease management as neurological sequelae in 20-25% is due to delay in diagnosis. Most of the existing TB tests like real-time PCR is beneficial but requires expensive equipment and expertise, limiting its use to highly sophisticated facilities.

LAMP (loop-mediated isothermal amplification ) is a highly sensitive and specific TB test. The reaction takes only one hour and can be conducted under isothermal conditions (ranging from 60-650C), eliminating the need for specialized equipment or expertise. Therefore this TB test can be performed even in a rural setting and specific for TB diagnosis.
PGI doctors had earlier conducted a study “Evaluation of the TB-LAMP assay for the rapid diagnosis of pulmonary tuberculosis in Northern India” which appeared in International Journal of Tuberculosis and lung diseases.

It was performed to evaluate a commercial kit-based loop-mediated isothermal amplification (TB-LAMP) assay for the diagnosis of pulmonary tuberculosis (PTB). In the study, the TB-LAMP assay showed high sensitivity and specificity with a limited requirement of testing infrastructure and was thus found to be a promising diagnostic tool for TB diagnosis in resource-poor settings.
Prof Sharma has customised the test and made it more sensitive.  “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 to  Times of India. 

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 the 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 a 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. 

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Source: With inputs from The International Journal of Tuberculosis and Lung Disease

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  1. user
    Dr Narendranath Sarkar November 9, 2018, 12:17 am

    Congratulations Dr Kusum Sharma.

  2. user
    Dr. Vidita Ghule October 30, 2018, 5:54 pm

    Congrats Dr. Sharma. I hope your hard work to bring to the door step of those patients in whom TB is more common, this LAMP of hope to quick diagnosis and prompt treatment! Hope all hurdles to availability of lamp test be tackled with sensitively for the benefit of rural patients… Good luck!

  3. user
    dr narendra gemawat October 29, 2018, 8:51 pm

    Congratulations Dr Sharma
    TB LAMP test for extra pulmonary tuberculosis should be a boon for clinician specially pediatricians as it\’s real a diagnostic dilemma in the era of evidence based Medicine as clinical medicine has taken a bit of back seat.

  4. user
    Dr Manisha Nagpal October 29, 2018, 2:02 pm

    Indeed very beneficial for diagnosing extra-pulmonary cases. such new innovations should always be supported

  5. TB LAMP test is one of the nucleic acid amplification test, originally innovated and reported by Notomy et al in the year 2000 though it was commercially used from 2013. Undoubtedly its detection sensitivity is much superior to PCR test and detection timing is shorter. However the sensitivity and specificity of these tests are highly variable, thus diagnostic accuracy is not clinically meaningful. The use of different cutoff values and the use of specimens other than sputum could explain some of the observed heterogeneity.

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