New Delhi, April 4 Moving beyond the traditional sputum tests, a new study on Friday showed that a molecular stool test may increase detection of tuberculosis (TB) in people living with HIV.
The research, published in the journal The Lancet Microbe, showed that using a molecular test (called Xpert MTB/RIF Ultra), currently used on respiratory samples, on stool samples -- until now recommended only for children -- could be established as an additional test for diagnosing TB in adults living with HIV.
It could represent a paradigm shift in the diagnosis of the disease in this population, said the team of researchers led by Barcelona Institute for Global Health (ISGlobal), Spain.
“People living with HIV are at higher risk of developing pulmonary TB, but diagnosis in these cases is particularly challenging due to the low sensitivity of conventional tests,” explains George William Kasule, a doctoral student at ISGlobal and the University of Barcelona, and the first author of the study.
TB, caused by the bacterium Mycobacterium tuberculosis, was responsible for 1.25 million deaths in 2023. Of these, 13 per cent were among people living with HIV.
Currently, the main diagnostic strategy for TB focuses on sputum samples -- obtained by deep coughing and expectoration of secretions produced in the lungs. For people living with HIV, a molecular sputum test is recommended in addition to urine antigen detection (TB-LAM).
However, these diagnostics are not effective for all people living with HIV, as they often struggle to produce sputum, and more than half of those in advanced stages of the disease are unable to do so.
Moreover, the concentration of bacteria in the sputum is often so low that it is undetectable.
To tackle this, the new research focused on stool samples. The team recruited 677 patients over 15 years old with HIV and suspected TB in medical centres in three African countries -Eswatini, Mozambique, and Uganda between December 2021 and August 2024.
Participants provided sputum, urine, stool, and blood samples.
The results showed that the stool test had a sensitivity of 23.7 per cent and a specificity of 94.0 per cent, compared with the reference standard.
“The results of our study support the use of the Stool Ultra test as a complementary tool for diagnosing tuberculosis in people living with HIV, especially in those with advanced AIDS, where the risk of tuberculosis is higher,” said Alberto L. Garcia-Basteiro, a researcher at ISGlobal and head of the Vaccine and Immune Response to Infections Unit at Hospital Clínic de Barcelona.
The Stool Ultra test identified additional cases that were not detected by TB-LAM, Ultra in sputum, or bacterial culture. Most importantly, it could confirm the disease in many cases where respiratory tests are negative.
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