July 22, 2009

ARV Treatment Eases Cape Town TB Rates

Wider use of antiretroviral (ARV) therapy during the past three years has significantly reduced the rate of tuberculosis (TB). This encouraging news was reported Wednesday, July 22, at the Fifth International AIDS Society (IAS) Conference on HIV Pathogenesis, Treatment and Prevention in Cape Town.

The HIV epidemic is driving TB epidemics to alarming rates in sub-Saharan Africa, said lead study author Keren Middelkoop, MD, of the Desmond Tutu HIV Centre at the University of Cape Town. Though it has been suggested that more widespread use will reduce the incidence and prevalence of TB, few data are available to confirm this hypothesis.

In 2005, Middelkoop’s group documented a high rate of undiagnosed TB before large-scale ARV availability, in a community with high HIV prevalence. In this analysis, HIV-positive individuals had a higher proportion of undiagnosed TB compared with HIV-negative individuals.

Middelkoop’s presentation at IAS focused on a 2008 follow-up survey, using similar methodology to the 2005 study. A random population was enrolled in the study, with each individual providing a completed survey and two phlegm samples for Mycobacterium tuberculosis testing. Rapid oral HIV testing was also conducted.

The average age of the 1,259 participants was 29 years. About 50 percent were female, and the HIV prevalence rate was 25 percent. Thirty-one percent of those living with HIV enrolled in the study were receiving ARV therapy.

The analysis reported by Middlekoop compared 310 HIV-positive individuals evaluated in the 2008 study with 175 in the 2005 study. It also compared 949 HIV-negative individuals from the 2008 study with 584 HIV-negative individuals from the 2005 study.

In 2005, about 4 percent of the HIV-positive volunteers were on treatment for tuberculosis and 5.2 percent had undiagnosed and untreated TB. In 2008, these rates dropped to 1.3 and 1.6 percent, respectively. Overall, Middelkoop reported, the tuberculosis rate among HIV-positive individuals dropped from 9.2 percent in 2005 to 2.9 percent in 2008—a statistically significant finding.

Rates among HIV-negative individuals remained fairly constant and, in fact, may have risen slightly. Overall, the tuberculosis rate was 1.2 percent in 2005 and 2.0 percent in 2008 among those uninfected with HIV. This difference, however, was not statistically significant.

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