Over-reliance on smear microscopy for TB detection continues Premium

India's TB testing rates and methods show progress but fall short of government targets, highlighting the need for improved diagnostics.

The presumptive TB testing rate in the country increased from 1,352 per lakh population in 2022 to 1,710 per lakh population in 2023. However, even two years before the 2025 deadline that the government has set to “eliminate” TB in India, only 21% of presumptive TB testing in 2023 was upfront done using a rapid molecular diagnostic test. According to the India TB Report 2024, which is yet to be made public, at 79%, the vast majority of presumptive TB testing was still carried out using the 100-year old sputum smear microscopy, which has low sensitivity. Ironically, compared with 2022, there has actually been a marginal decrease ­— from 23% to 21% ­— in the percentage of presumptive TB testing offered upfront using a molecular test in 2023.

The number of molecular testing facilities in the country has increased from 5,090 in 2022 to 6,496 in 2023. Also, there was a small increase in the rate of molecular testing in 2023 compared with 2022; the number of rapid molecular tests offered for presumptive TB testing increased from 292.7 per lakh population in 2022 to 358 per lakh population in 2023. However, this has not been reflected in an increase in the proportion of molecular testing last year compared with 2022. India has still a long way to go before it reaches the goal of offering a molecular test upfront to all presumptive TB patients, with nil reliance on smear microscopy.

In 2023, 37.19 lakh patients were offered a CBNAAT test, of which 7.4 lakh people were diagnosed with TB, representing a yield of 20%. In the case of TrueNat, of the 31.13 lakh patients who were tested using TrueNat, 3.3 lakh persons were diagnosed with TB, representing a yield of 11%. For smear microscopy, of the 1.89 crore persons tested, only 5.78 lakh were diagnosed with TB, representing a yield of just 3%.

The National Strategic Plan 2017-2025 wanted to reduce the number of presumptive TB patients who are offered sputum smear microscopy from over 9.1 million in 2015 to 5.1 million in 2023, while increasing the number of molecular tests from 40,000 in 2015 to over 14.7 million in 2023. However, as per the India TB report, in 2023, India was far from reaching the ambitious target set by NSP 2017-2025. The overreliance on smear microscopy has continued in 2023 with 79% of presumptive TB cases detected using smear microscopy and just 21% cases detected using a molecular test.

The revised National Strategic Plan 2020-2025 has raised the bar even higher for precision tests to be used for initial diagnosis. Four years after the launch of the revised NSP, India is nowhere near meeting the targets. One of the main objectives of the revised NSP 2020-2025 is the early detection of presumptive TB cases. It clearly says there should be “prompt diagnosis” using highly sensitive diagnostic tests for detecting presumptive TB cases “at the first point of contact” both in the private and public sectors. 

Universal drug-susceptibility testing in all drug-sensitive TB cases is crucial for early identification of drug-resistant TB. The revised NSP 2020-2025 clearly states that NTEP should provide “universal access” to drug resistance testing. However, in 2023, the proportion of notified TB patients offered drug-susceptibility testing was just 58% as against the target of 98%. In the absence of drug-susceptibility testing, it is not possible to ascertain drug-resistant cases and offer them suitable MDR-TB medicines.