Use of Antiretroviral Therapy Associated with a Large Decrease in Tuberculosis
Prevalence in South Africa|
availability of antiretroviral drugs through a scaled-up treatment program has
contributed to a dramatic decline in TB rates especially among HIV positive people
in a low-income community in South Africa, according to a presentation at the
5th International AIDS Society Conference on HIV Pathogenesis, Treatment, and
Prevention (IAS 2009) this week in Cape Town. |
acts as an opportunistic illness
in people with HIV, and the widespread AIDS
epidemic in South Africa is associated with a concurrent epidemic of TB, as well
as outbreaks of multidrug-resistant (MDR-TB) and extensively drug-resistant (XDR-TB)
immune suppression increases the risk of developing active TB disease, and conversely,
effective combination antiretroviral
therapy (ART) has been shown to improve outcomes in HIV-TB coinfected individuals.
outside Cape Town
(Photo: Liz Highleyman)
(Photo: Liz Highleyman)
Middelkoop from the Desmond Tutu HIV Centre in Cape Town and colleagues undertook
a study to see whether ART would have a beneficial effect on TB rates at the population
level. The investigators assessed HIV and TB rates over time in a township outside
Cape Town with a population estimated at 15,000 people.
community has a well-functioning TB prevention and treatment program based on
short-course directly observed therapy (DOTS), and was included in an effort to
roll out and scale up HIV treatment starting in the mid-2000s. All TB patients
in the community are treated at a single clinic. National program guidelines for
diagnosis and management of TB did not change significantly over the study period.
2008, nearly one-quarter of the HIV positive population was receiving antiretroviral
drugs double the proportion on treatment in 2005 representing about 90% of patients
who need ART according to local guidelines (based on a threshold of 200 cells/mm3
or symptomatic disease, including active TB).
researchers reported that annual TB reporting rates increased significantly between
1998 and 2004, coinciding with an increased rate of HIV infections over the same
period. TB notifications peaked in 2005, the year the widespread ART roll-out
began possibly attributable to increased TB screening of individuals seeking ART
and thereafter started to decline.
2005 and 2008, the researchers conducted cross-sectional surveys of random samples
of adults in the community (762 people in 2005 and 1251 in 2008). The mean age
was about 30 and men and women were equally represented. Participants received
sputum smears to test for TB as well as oral HIV testing.
on the 2005 survey, the investigators previously reported a high prevalence of
undiagnosed TB prior to widespread ART availability, with HIV positive individuals
being more likely than HIV negative people to have undiagnosed TB. In a late-breaker
oral presentation at this week's conference they reported follow-up date from
the 2008 survey.
the cross-sectional surveys, TB prevalence fell from 3% of sampled participants
in 2005 to 1.8% in 2008.|
this same period, HIV prevalence among surveyed individuals rose slightly, from
23% to 25%.|
HIV positive people, TB prevalence fell from 9.2% to 3.6% after the ART roll-out
(P = 0.02).|
HIV negative individuals, however, the rate remained stable at around 1%.|
previously undiagnosed TB cases among HIV positive people decreased from 5.2%
to 1.3% (P = 0.01).|
too, the rate of undiagnosed among HIV negative participants stayed the same,
at around 0.5%.|
notification rates for the population declined markedly from 2005 to 2008, but
again the decrease was mostly attributable to HIV positive individuals.|
overall TB reporting rate fell from about 2500 to about 2000 cases per 100,000
HIV positive participants, the rate decreased from about 7000 to about 5300 per
HIV negative people, the rate fell from about 1000 to about 500 per 100,000 PY.|
availability of ART appears to be associated with a decrease in prevalence of
microbiologically confirmed TB in this community, predominantly in the HIV-infected
population," the investigators concluded.
researchers noted that there were no changes in TB program practices, death rates,
or numbers of people leaving the community that could explain the decrease in
TB seen in this study. TB-related mortality, in fact, decreased, especially among
HIV positive people.
added that the decline in TB could be attributable to a lower TB transmission
rate (due to fewer infected individuals in the population), less reactivation
of latent disease due to improved immune function, or some combination of these
of Cape Town; Desmond Tutu HIV Centre, Institute of Infectious Disease and Molecular
Medicine, Cape Town, South Africa; University of Cape Town, School of Public Health
& Family Medicine and Department of Clinical Laboratory Sciences, Cape Town,
South Africa; Columbia University, Department of Epidemiology, Mailman School
of Public Health, New York, National Health Laboratory Service, Cape Town, South
Africa; University of Medicine and Dentistry of New Jersey, Public Health Research
Institute, New Jersey; University of the Witwatersrand, Perinatal HIV Research
Unit, Johannesburg, South Africa.
Middelkoop, R Wood, L Myer, and others. Widespread ART is associated with decline
in TB prevalence. abstract WeLBB105, 2009. 5th International AIDS Society Conference
on HIV Pathogenesis, Treatment, and Prevention. July 19-22, 2009. Cape Town, South
Africa (IAS 2009). Abstract WeLBB105.
Middelkoop, R Wood, L Myer, and others. Can antiretroviral therapy contain a previously
escalating TB epidemic in a high HIV prevalence community? 5th International AIDS
Society Conference on HIV Pathogenesis, Treatment, and Prevention. July 19-22,
2009. Cape Town, South Africa (IAS 2009). Abstract CDB041.