Antiretroviral therapy as prevention: TB

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Stephen Lawn reminded the audience at the International Treatment as Prevention Workshop in Vancouver on Wednesday that antiretroviral therapy (ART) goes a long way to protect HIV-infected individuals from tuberculosis (TB). The HIV-associated TB epidemic requires “radical interventions,” according to Lawn.  “DOTS [directly observed TB therapy, short course] just isn’t doing it.”

He called the protective benefit of ART a “largely CD4-associated benefit,” because increasing the CD 4 count as high as possible is key to the protective effect.  ART scale-up in Cape Town, South Africa, has reduced the risk of TB by two-thirds.  Nevertheless, persons with HIV infection remain at higher risk of TB acquisition than their HIV-negative counterparts.  There continues to be a five percent annual risk of developing tuberculosis. There are other side benefits as well, since there is the potential for intensified TB case finding in ART clinics and the opportunity to use the ART clinic as a platform for administering isoniazid preventive therapy (IPT), which combined with ART, further lowers TB risk.

We need to start ART earlier since many patients never recover a full complement of CD4 cells, especially if treatment is delayed, Lawn said.  Starting ART sooner after HIV seroconversion could have an even more dramatic impact on HIV-associated TB, with a potential 95 percent reduction in risk if initiated within two years of HIV seroconversion.

ART also protects against drug-resistant TB. Lawn pointed out that the majority of patients infected with extensively drug-resistant TB (XDR-TB) in Tugela Ferry, South Africa, had very low CD4 counts and were not on ART. 

Haileyesus Getahun from the World Health Organization (WHO) acknowledged that we need to do a better job in getting HIV-infected people with TB on ART.  In most countries, TB treatment is decentralized and there are many more sites—sites that could provide a platform to decentralize ART provision for this population. Getahun, who leads the TB/HIV team at the WHO, also reminded us that Africa is not the only part of the world where HIV-associated TB is a big issue.  In parts of Eastern Europe and Central Asia there is a convergence of tuberculosis, HIV infection, hepatitis and drug use, especially in prisons.  This “fatal synergy,” according to Getahun, could certainly be ameliorated through greater ART scale-up.

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