Indigenous TB test can enhance accuracy, speed up testing

The rt-LAMP assay is a molecular test with excessive sensitivity and specificity
| Photo Credit: CDC/ Ray Butler, MS

Researchers on the Thiruvananthapuram-based Sree Chitra Tirunal Institute for Medical Sciences and Technology (SCTIMST) have developed and examined a novel, cost-effective, real-time LAMP (rt-LAMP) assay for early analysis of TB. Much like GeneXpert and Truenat, the rt-LAMP assay too is a molecular test with excessive sensitivity and specificity. The rt-LAMP assay was capable of detect TB DNA even when solely 10 copy numbers have been current per microlitre in a pattern. 

The primary handicap that prevented the usage of LAMP for TB analysis thus far was the shortcoming of utilizing any dye, as dyes usually inhibit response resulting in false negatives. Researchers at SCTIMST have overcome this problem by turning to a fluorescent dye Syto 16, which is routinely utilized in labs for learning cells and different organic samples. And in contrast to RT-PCRs that require three completely different temperature settings to finish a test, the rt-LAMP test works at a single temperature. Since a fluorescent dye is used, the amplification can be measured not on the finish of the run however each minute. 

“With six primers used for amplification compared with two in the case RT-PCRs, the rate of amplification is high, and hence results of positive samples can be obtained in 10-20 minutes,” says Dr. Anoopkumar Thekkuveettil from SCTIMST and the corresponding writer of a paper printed in Scientific Reports. “Since all six primers need to bind to the DNA for amplification to begin, the rt-LAMP assay has very high specificity.” Since no probe is used in contrast to within the case of RT-PCR exams, and because the dye and primers are cheap, the rt-LAMP test turns into extremely reasonably priced. 

The assay was examined on 350 presumptive pulmonary TB sputum samples. The rt-LAMP package was evaluated towards a microbiological reference commonplace (MRS), GeneXpert, and smear test. The examine was performed from October 2019 to March 2020 and from January 2023 to March 2024. The rt-LAMP assay demonstrated barely greater sensitivity and specificity than the GeneXpert assay. Compared with MRS, rt-LAMP confirmed 89.36% sensitivity and 94.06% specificity. 

“The rt-LAMP assay kit has been developed as an open platform system which allows existing RT-PCR machines to be repurposed for TB diagnosis. This can be done by programming an existing RT-PCR machine to run at one temperature setting instead of three,” Dr. Anoopkumar says. “It is possible to process up to 96 or 384 tests in a single run. Thus the assay facilitates high throughput testing, allowing for a large number of patient samples to be processed in a single run.”

“The technology has been licensed to industry, has received approval from CDSCO, and is currently being validated by ICMR. The WHO Health Technology Access Pool program is currently evaluating the technology and is waiting for ICMR validation,” he says.

With almost 79% of presumptive TB instances in India recognized utilizing sputum smear microscopy and solely 21% examined utilizing molecular assay as not too long ago as 2023, India continues to over-rely on smear microscopy for TB analysis. Despite a rise in molecular testing amenities from 5,090 in 2022 to six,496 in 2023, it’s nowhere near assembly the National Strategic Plan 2017-2025 of decreasing the reliance on smear microscopy.