Goa’s 100% Molecular Testing Helps Early TB Detection

Sputum microscopy simply means looking for the rod-like TB bacteria under the microscope. This method is fast and cheap but has very low sensitivity (40-60%) as it requires a higher number of bacilli to be detected. This means that about half the cases are not detected. It also has lower sensitivity for TB in children, and patients with HIV and extrapulmonary TB.

Nucleic Acid Amplification tests (NAATs), on the other hand, are rapid tests that can identify the genetic material of the TB bacteria and are more than 90% sensitive and accurate. These tests can also detect resistance to rifampicin, one of the major TB drugs. For NAAT testing, Indian public health systems have GeneXpert from US-based Cepheid or Truenat from Goa-based Molbio Diagnostics.

Before Goa started upfront NAAT testing, they used to diagnose most of the TB cases in the medical college, said Manish Gaunekar, Goa state TB officer. The use of NAAT testing has improved detection at the peripheral centres, from less than 50% of all cases in 2019 to 62% in 2023.

Source: Goa TB department

Goa, which started ramping up molecular testing in 2020, is the only state with 100% NAAT testing, as per the 2024 India TB report. Ladakh (93%) and Meghalaya (81%) follow.

Goa has four GeneXpert systems and 17 Truenat systems in its public health facilities. Truenat runs on a portable, battery-operated platform and can be taken to peripheral health centres situated at difficult terrains with irregular electric supply.

Universal access to World Health Organization (WHO)-recommended rapid tests for all is one of the new targets set by WHO’s Director-General’s flagship initiative to end TB by 2027. As per the India TB report 2024, only 21% of presumptive TB tests were used doing NAT.

Presumptive TB Examination Rates In India

Figures are in tests per 100,000 population

Source: India TB report, 2024

Reduces delay in diagnosis

Researchers model the TB care cascade to estimate gaps, as IndiaSpend reported in May 2023. The number of patients with incident TB who did not access TB tests constitute gap 1, patients who did not get diagnosed constitute gap 2, those who did not register for treatment constitute gap 3, those who were not successfully cured comprise gap 4, and those who relapsed or died even after being treated constitute gap 5.

India's most significant gap in the cascade of care in TB is diagnosis of the disease itself, we had reported. As per the National TB Prevalence Study, 2019-21, a majority of the symptomatic population--about 64%--did not seek healthcare services. The reasons are either they ignore the symptoms, or they don't recognise the symptoms as TB or they cannot afford to seek care. So it is imperative that the patients who do seek care should be tested and diagnosed as soon as possible so that they do not fall off the TB care net.

Before 2020, if a patient from Goa was symptomatic, they would first undergo sputum microscopy. If this was negative--which happens about 50% of the time even if the patient has TB--they would have to go to a higher centre such as a district hospital or medical college, losing at least about one-and-a-half to two months, said Gaunekar.

“Our patients are mostly migrant workers or old people,” said Smita Parsekar, health officer at Ponda’s primary health centre. Ponda is about 32 km from Goa Medical College, in Panaji. “They used to waste a lot of time in big hospitals for getting TB tests where one has to spend a whole day in the hospital and even come for follow up.”

“By this time the bacilli would rise and the patient would become more infectious,” said Gaunekar. “The microscopy would be able to pick it up the second or third time. Now what is happening is that infection is being picked right in the beginning at the primary healthcare facility itself.”

In the National TB Prevalence Survey, 33% of cases were exclusively diagnosed based on the NAAT test. Exclusive sputum microscopy only yielded 7.9% of cases. The Survey recommends prioritising molecular test coverage.

Easier follow up

The availability of a quick testing method helps increase TB notification and in collecting data that can be used by TB officers to analyse the issues in the population. Goa has a higher TB death rate--about 8.3% in 2022 as opposed to the all India mortality rate figure of 3.9%, as IndiaSpend reported on October 22. In 2023, this climbed to 9.6%.

“Since we audit TB deaths, we have realised that people are dying within five days of admission,” said Govind Desai, South Goa TB officer. “Because we are diagnosing them sooner, we can record them as TB deaths.”

The availability of a superior testing method in the primary health centres has also resulted in private doctors sending their patients for TB testing there. “In my area, that is Ponda, we have about 3-4 villages around the PHC,” said Parsekar. “Many private doctors here are referring their patients with TB symptoms to the PHC

Even follow up of patients has become faster. If the diagnosis is done in hospitals, for them to inform the primary health centre or sub-centre that directly follows up with patients--with home visits and doorstep treatment--can take at least a week if not more,” she said.

We welcome feedback. Please write to respond@indiaspend.org. We reserve the right to edit responses for language and grammar.