ART reduces TB risk, even in high-income countries
However, the benefit is not seen in patients who start ART at very low CD4-cell counts
Quantifying the effect of antiretroviral therapy (ART) on the incidence of tuberculosis (TB) in HIV-infected patients has been difficult. Several studies have shown a lower rate of TB among HIV-infected patients who are receiving ART than among those who are not. However, during the first few months of treatment, TB rates may be elevated because of immune reconstitution inflammatory syndrome (IRIS).
In the present study, investigators estimated the effect of ART on TB incidence in high-income countries, using data from 12 cohorts in Europe and the U.S. The analysis was limited to 65,121 HIV-infected patients who were antiretroviral-naive at the time of enrollment, between 1996 and 2007.
During a median follow-up of 28 months, 712 patients received a TB diagnosis, for an incidence rate of 3 cases per 1000 person-years. Overall, the incidence of TB was significantly lower among patients who were receiving ART than among those who were not (hazard ratio, 0.56), but the effect varied across subgroups and according to time since ART initiation. During the first 3 months of ART, patients had an increased risk for TB, particularly if they had a baseline CD4 count <50 cells/mm3 (HR, 2.3) or were older than 50 (HR, 3.2). In subsequent months, this association was reversed (HR, 0.44), but the benefit did not extend to patients who started ART at CD4 counts <50 cells/mm3 or after age 50.
Comment: The optimal timing of ART initiation in patients with HIV/TB coinfection became clearer last fall, after the publication of three randomized, controlled trials (JW AIDS Clin Care Oct 19 2011). The current study demonstrates the importance of ART as a means of preventing TB among HIV-infected patients, even in high-income countries. However, this protective effect is negated in patients who start ART at very low CD4 counts (<50 cells/mm3) or after age 50, giving us yet another reason to diagnose and treat HIV infection early. Perhaps the time has come in high-income countries that starting ART at a CD4 count <50 cells/mm3 should be considered a "sentinel event."
Published in Journal Watch HIV/AIDS Clinical Care May 14, 2012
Citation(s):
The HIV-CAUSAL Collaboration. Impact of antiretroviral therapy on tuberculosis incidence among HIV-positive patients in high-income countries. Clin Infect Dis 2012 May 1; 54:1364.
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http://aids-clinical-care.jwatch.org/cgi/content/full/2012/514/1?q=featured_ac
