HIV positive people in low and middle income countries who are taking anti-HIV drugs (antiretroviral therapy) are significantly less likely to develop tuberculosis compared to those who are not taking antiretroviral therapy.
This is according to a new study by a group of international researchers led by Dr Amitabh Suthar of the World Health Organisation, to be published in the open access journal PLoS Medicine. The group of international researchers includes Dr Brian Williams, formerly from the WHO and now associated with the South African Centre for Epidemiological Modelling and Analysis (SACEMA) based at Stellenbosch University, and Dr Stephen Lawn of the Desmond Tutu HIV Centre oat the University of Cape Town and the London School of Hygiene and Tropical Medicine. Other researchers are affiliated with the John Hopkins University School of Medicine (USA) and the National Centre for Epidemiology (Spain).
What the study found
The study found that ARVs protects against tuberculosis irrespective of the CD4 count (a biomarker of immunodeficiency) at which HIV positive people start taking antiretroviral therapy.
The protective effect was also seen in adults with CD4 counts above 350 cells/mL. (The World Health Organization currently recommends antiretroviral therapy in adults with CD4 counts below 350 cells/mL).
“People who are HIV positive are extremely susceptible to tuberculosis because the HIV virus destroys the immune system cells that are necessary to combat tuberculosis infection,” says Dr Suthar and colleagues.
In 2010, there were 1.1 million new cases of tuberculosis among 34 million people living with HIV and 350,000 people died of HIV-associated tuberculosis, making tuberculosis the leading cause of death among HIV-positive people.
The paper in PLoS Medicine combines 11 relevant studies from Sub-Saharan Africa, South America, the Caribbean, and Asia. It found that study participants taking antiretroviral therapy had a 65% reduction in their risk of developing tuberculosis relative to study participants who were not receiving antiretroviral therapy, irrespective of the CD4 count at which they started taking antiretroviral therapy.
Importantly, the authors found that taking antiretroviral therapy was associated with a 57% reduction in tuberculosis risk among adults with CD4 counts greater than 350 cells/mL. Currently the World Health Organisation recommends antiretroviral therapy below this threshold in adults with HIV.
“This review found that antiretroviral therapy is strongly associated with a reduction in tuberculosis incidence in adults with HIV across all CD4 cell counts,” says Dr Suthar and colleagues in the paper titled “Antiretroviral Therapy for Prevention of Tuberculosis in Adults with HIV: A Systematic Review and Meta-Analysis”.
The key findings
“Our key finding that antiretroviral therapy has a significant impact on preventing tuberculosis in adults with CD4 counts above 350 cells/ml is consistent with studies from developed countries,” they say. “This need to be considered by healthcare providers, researchers, policymakers, and people living with HIV when weighing the benefits and risks of initiating antiretroviral therapy above 350 cells/ƒÝL.”
“Earlier initiation of antiretroviral therapy may be a key component of global and national strategies to control the HIV-associated tuberculosis syndemic,” said Dr Suthar and colleagues.
Dr Williams agrees with this. “Our studies over the years in various African countries have shown that we need to start our intervention with HIV positive people as early as possible, to help curb the spread of HIV and its related consequences.”
(Press release, July 2012)
HIV/Aids and TB