A simple change in the drug regimen used to prevent active tuberculosis disease among HIV-positive people who test positive for latent TB infection can drastically reduce TB-related illness, suggests a study by the Centers for Disease Control and Prevention.

To prevent latent TB infection from progressing to active TB disease, the World Health Organization (WHO) recommends six months of isoniazid preventive therapy (IPT) for HIV-infected individuals who also test positive for latent TB infection. However, the study found that by extending the standard six month IPT regimen to 36 months, patients experienced a 92 percent reduction in their risk for developing active TB disease. Latent TB infection occurs when a person has TB bacteria in their body, but does not become sick because the bacteria are not active. Active TB disease, on the other hand, occurs when the bacteria multiply and destroy tissues in the infected person's body.

The study was conducted in Botswana, where 80 percent of TB patients are co-infected with HIV, compared to seven percent in the United States, and presented today at the 2010 Conference on Retroviruses and Opportunistic Infections in San Francisco.

"These findings have profound implications for Botswana and other nations where both HIV and TB are widespread," said Kevin Fenton, M.D., director of CDC's National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention. "TB remains the leading killer of HIV-infected individuals worldwide. This study demonstrates that providing ongoing therapy could significantly reduce its impact."

Study authors conclude that in countries such as Botswana, where TB is widespread, health care providers should consider prescribing IPT for at least 36 months to persons with HIV and a positive tuberculin skin test.

CDC began the $12 million randomized placebo-controlled trial in Botswana in 2004 to help identify new methods to reduce the severe toll of TB among the nation's large HIV-infected population. The Botswana government estimates that 25 percent of the population aged 15-49 is infected with HIV, and that 40 percent of deaths among people with AIDS are caused by TB.

Two thousand HIV-infected participants were enrolled in the study, 24 percent of whom tested positive for latent TB infection. Half of the participants received six months of IPT followed by 30 months of placebo, and the other half received daily IPT for 36 months. Participants received antiretroviral therapy (ART) according to Botswana government guidelines during the course of the study. Because ART is also known to reduce development of TB and other opportunistic infections, researchers controlled for ART use in the analysis.

Among participants who tested positive for latent TB infection, 2.53 percent of those taking the six month IPT regimen developed TB disease each year, compared to only 0.19 percent of those taking the 36 month IPT regimen. Those participants who did not test positive for latent TB infection derived no benefit from either IPT regimen.

TB - a communicable disease which can be fatal if not treated - usually affects the lungs, but can also affect other parts of the body, such as the brain, kidneys, or spine. According to the WHO, more than 9 million people around the world become sick with TB, and almost 2 million die, each year. In some areas, TB is an epidemic, with hundreds of thousands affected in nations such as China, India, and Vietnam, and in many countries of sub-Saharan Africa.

Source
Centers for Disease Control and Prevention