A groundbreaking study reveals a promising new method for detecting tuberculosis in HIV-positive adults using molecular stool testing. Traditional sputum tests often fail for patients with advanced HIV, creating significant diagnostic challenges. The research, conducted in Eswatini, Mozambique, and Uganda, demonstrates that the Stool Ultra test can identify TB cases missed by conventional methods. This innovative approach could significantly improve early detection and treatment for vulnerable populations living with HIV and tuberculosis.
April 04, 2025
Molecular stool test shows promise for TB diagnosis in adults with HIV: Study
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.
Key Points
1 Molecular stool test shows 23.7% sensitivity for
TB diagnosis
2 New method helps HIV patients unable to produce
sputum
3 Study conducted across three African countries
4 Complements existing TB diagnostic strategies
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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