HIV-Positive Individuals Previously Cured of TB Have Greater Risk of TB Recurrence Than People Without HIV, Study Shows
HIV-positive individuals who have successfully completed tuberculosis treatment have a greater risk of experiencing a recurrence of TB than those without HIV infection, according to a study in the Nov. 17 issue of the Lancet. Pamela Sonnenberg of the London School of Hygiene and Tropical Medicine and colleagues studied 326 South African goldmine workers who had previously been cured of pulmonary TB. To chart the rate of TB recurrence -- which can be attributed to either relapse or reinfection -- participants were examined three and six months after being cured and were then monitored until either Dec. 31, 1998, the date they left the mine, or death, whichever occurred first. Risk factors such as HIV status, CD4+ cell count, demographics and lifestyle were also analyzed. Only patients who had been cured of TB and whose initial infection did not occur from a multidrug-resistant strain of the disease were included in the study. No patients received antiretroviral therapy. The study findings include the following:
- Of the 326 participants, 151 were HIV-positive and 175 were HIV-negative.
- Forty-one of the HIV-positive participants suffered a recurrence of TB, compared to 24 HIV-negative participants.
- The recurrence risk for HIV-positive patients was calculated to be 16 episodes per 100 person-years at risk, compared to 6.4 episodes for 100 person-years at risk for HIV-negative participants.
- Of the 41 recurrences among HIV-positive participants, 13 were due to reinfection, eight were due to relapse and 20 were attributed to unknown causes. Among HIV-negative participants, 17 of the 24 recurrences were due to relapse, one was due to reinfection and six were attributed to unknown causes.
- HIV-positive individuals were found to be 2.4 times more likely to have a recurrence of TB as HIV-negative individuals and were 18.7 times more likely to have a recurrence due to reinfection. HIV infection was found to be "the only significant risk factor for reinfection."
- There was no significant difference in the rates of relapse between HIV-positive and HIV-negative participants.
- CD4+ cell count in HIV-positive patients was not linked to TB recurrence.
- HIV-positive patients were more likely to have died during the study than HIV-negative patients.
The study states that HIV infection was found to be a risk factor for TB recurrence because HIV is strongly associated with disease caused by reinfection. People with HIV could be at high risk for developing TB after exposure to the bacteria, and those who have had TB might have low immunity to subsequent infection. However, immunosuppression in HIV-positive participants was not found to increase the risk of TB recurrence, possibly because patients with advanced immunosuppression die from other causes before the development of recurrent TB, the authors write. To fight recurrent TB among people with HIV, medical officials should investigate options in chemotherapy. "Agressive" primary chemotherapy, as well as secondary chemoprophylaxis for up to one year, could reduce the risk of TB recurrence. The researchers propose the possibility of lifetime chemotherapy for individuals who have been cured of TB but who are in situations that carry a high risk of TB infection (Sonnenberg et al., Lancet, 11/17).