Tuberculosis is one of the deadliest infectious diseases. In 2020, some 9.9 million people worldwide fell ill with this disease and an estimated 1.5 million died.
The arrival of HIV in the 1980s triggered a huge increase in tuberculosis, especially in sub-Saharan Africa. In some countries, the number of people diagnosed with tuberculosis has quadrupled each year. People with HIV are especially susceptible to tuberculosis.
My colleagues and I are part of a research project called Tuberculosis reduction through scale-up of antiretroviral treatment and detection of active tuberculosis; Treats for its acronym in English. The project set out to test whether a “universal test and treat” approach in Zambia and South Africa could achieve a strong reduction in HIV and tuberculosis.
This approach had been used in an HIV and TB intervention known as PopART, short for Population effects of antiretroviral therapy in reducing HIV transmission. We expected to find that screening for tuberculosis worldwide would identify individuals with the disease who had not yet been diagnosed. We also thought that treating them quickly would reduce the amount of infection in the community and the risk of infection to others.
But it was not like that. Worldwide tuberculosis screening had no impact on the prevalence or incidence of tuberculosis infection. The reasons are complex and our team is in the early stages of analyzing the results to identify possible explanations.
The PopART intervention took place between 2013 and 2018. It offered combined testing and treatment for HIV and tuberculosis to some 600,000 people in Zambia and South Africa. It was carried out by health workers who visited every home in an entire community at least once a year.
These community health workers provided information on both diseases. In addition, they offered everyone an HIV test and screened everyone for tuberculosis through a simple symptom screening.
People who presented symptoms suggestive of tuberculosis were asked for a sputum sample that was taken to a health center to carry out the test that would confirm the diagnosis.
Anyone who tested positive for HIV was encouraged to access antiretroviral therapy, which was provided to everyone regardless of CD4 cell count.
The PopART intervention was found to reduce HIV incidence by approximately 20% in communities that received the intervention compared to those that did not.
The TREATS study then followed up between 2017 and 2021 to measure the effect that the PopART intervention had on tuberculosis. A key component of the TREATS study was to measure whether PopART had reduced the overall prevalence of active tuberculosis. There were 50,000 participants, aged 15 and over. Community workers went door-to-door explaining the study and inviting people to get tested for HIV and tuberculosis in mobile units. A screening and testing site was set up that included a digital X-ray machine and a portable laboratory to identify tuberculosis in sputum samples.
More sensitive TB screening tools that are feasible, acceptable and affordable are urgently needed
The TREATS survey compared the prevalence of tuberculosis in communities that had received the PopART intervention with those that had not. No differences were found in the prevalence of the former. TREATS also measured whether youth in communities that received the intervention had fewer new TB infections than those in communities that did not receive the intervention. Again, no differences were found.
Tuberculosis screening used in the PopART intervention was based on symptom screening followed by sputum testing. This screening method, while feasible and acceptable, is likely to be insufficient to reduce the burden of tuberculosis. We know that some people with TB have no symptoms or don’t think their symptoms are worth mentioning. Chest radiographs are more sensitive for tuberculosis screening, but are largely unavailable and unaffordable in settings where tuberculosis disease is common.
More sensitive tools for tuberculosis screening that are feasible, acceptable and affordable are urgently needed.
Our study has highlighted the importance of addressing the stigma around TB and HIV to encourage people to seek diagnosis and treatment in these communities. Community health workers conducting the PopART visits found that as the rounds of the intervention continued, the stigma faded. People were happier to be tested for HIV and tuberculosis. In fact, the number of people who tested positive increased over time, which may be a reflection of people feeling safer.
But TREATS has shown that improvements in HIV diagnosis and treatment do not translate easily into greater success against tuberculosis. Further research will be essential to harness the lessons of TREATS and find the best way to fight this devastating disease.
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