Concurrent drug therapy for tuberculosis and HIV infection in resource-limited settings: present status and future prospects

Optimum time to start antiretroviral therapy during HIV-associated opportunistic infections

PURPOSE OF REVIEW

We review recently published literature concerning the optimum time to start antiretroviral therapy (ART) in patients with HIV-associated opportunistic infections.

RECENT FINDINGS

In addition to data from observational studies, results from six randomized controlled clinical trials were available by July 2010. The collective findings of these trials were that patients with CD4 cell counts less than 200 cells/μl who start ART within the first 2 weeks of treatment for opportunistic infections including Pneumocystis jirovecii pneumonia, serious bacterial infections or pulmonary tuberculosis have lower mortality when compared to patients starting ART at later time-points. Moreover, patients with pulmonary tuberculosis and CD4 counts of 200-500 cells/μl who started ART during tuberculosis (TB) treatment had improved survival compared to those who deferred ART until after the end of treatment. In contrast, in two separate studies, immediate ART conferred no survival benefit in patients with TB meningitis and was associated with substantially higher mortality risk in patients with cryptococcal meningitis.

SUMMARY

Initiation of ART during the first 2 weeks of treatment for serious opportunistic infections has been shown to be associated with improved survival with the exception of patients with tuberculous meningitis and cryptococcal meningitis. Further clinical trials are ongoing.

Tuberculosis during the first year of antiretroviral therapy in a South African cohort using an intensive pretreatment screening strategy

OBJECTIVE

To determine the baseline prevalence of tuberculosis (TB) in a cohort using a strategy of intensive pretreatment screening for TB and the subsequent incidence rate and temporal distribution of cases during the first year of antiretroviral therapy (ART).

DESIGN

Prospective observational community-based ART cohort in South Africa.

METHODS

Adults enrolling for ART and who did not have a current TB diagnosis were intensively screened for TB at baseline using culture of two sputum samples, chest radiography and investigations for extrapulmonary disease as required. Patients who developed symptoms consistent with incident TB during ART were similarly investigated.

RESULTS

Two hundred forty-one patients had a median CD4 cell count of 125 cells/microl (interquartile range 70-186) and 200 (83%) started ART. TB was diagnosed in 87 (36%) patients, with 82% of pulmonary cases being culture-proven. Most TB cases (87%) were prevalent disease detectable at baseline, whereas just 11 (13%) were incident cases that presented during the first year of ART. The incidence rate during 0-4 months of ART was similar to the rate during months 5-12 of ART [10.9 (95% confidence interval [CI] 4.6-23.3) cases per 100 person-years versus 8.1 (95% CI 3.6-18.0) cases per 100 person-years].

CONCLUSION

Systematic culture-based screening detected a very high burden of prevalent TB present at baseline. This intensified screening strategy was associated with an approximately two-fold lower incidence rate in the first 4 months of ART than previously observed in this cohort. This suggests that many incident cases of symptomatic TB presenting during early ART can be detected as prevalent disease prior to ART initiation using sensitive diagnostic tests.

Immune reconstitution disease associated with mycobacterial infections

PURPOSE OF REVIEW

We review immune reconstitution disease associated with mycobacterial infections in patients receiving antiretroviral treatment. We draw particular attention to data relevant to resource-limited settings and focus predominantly on publications over the past year.

RECENT FINDINGS

Worldwide mycobacteria are the most important group of pathogens associated with immune reconstitution disease. In cohorts of patients with tuberculosis in high-income countries, up to one-third develop immune reconstitution disease compared with only 8-13% in current reports from resource-limited settings. We speculate on potential explanations for this difference. While most cases of tuberculosis immune reconstitution disease are self-limiting, deaths have been reported in South African and Thai cohorts. We discuss how risk and outcomes of tuberculosis immune reconstitution disease represent key variables regarding the optimum time to initiate antiretroviral treatment in tuberculosis patients. A new conceptual framework has been proposed regarding 'unmasking' of tuberculosis during antiretroviral treatment. Increasing numbers of cases of leprosy immune reconstitution disease and Bacillus Calmette-Guérin immune reconstitution disease have also been reported, mainly from resource-limited settings. Immune reconstitution disease associated with a variety of mycobacteria (tuberculous and nontuberculous) was common in a cohort of Thai children.

SUMMARY

Immune reconstitution disease associated with a range of mycobacteria constitutes a challenge to delivery of antiretroviral treatment worldwide. Data concerning the pathogenesis and management of all forms of mycobacterial immune reconstitution disease are lacking.

Short-term and long-term risk of tuberculosis associated with CD4 cell recovery during antiretroviral therapy in South Africa

OBJECTIVE

To determine the short-term and long-term risks of tuberculosis (TB) associated with CD4 cell recovery during antiretroviral therapy (ART).

DESIGN

Observational community-based ART cohort in South Africa.

METHODS

TB incidence was determined among patients (n = 1480) receiving ART for up to 4.5 years in a South African community-based service. Updated CD4 cell counts were measured 4-monthly. Person-time accrued within a range of CD4 cell count strata (CD4 cell strata) was calculated and used to derive CD4 cell-stratified TB rates. Factors associated with incident TB were identified using Poisson regression models.

RESULTS

Two hundred and three cases of TB were diagnosed during 2785 person-years of observation (overall incidence, 7.3 cases/100 person-years). During person-time accrued within CD4 cell strata 0-100, 101-200, 201-300, 301-400, 401-500 and more than 500 cells/microl unadjusted TB incidence rates were 16.8, 9.3, 5.5, 4.6, 4.2 and 1.5 cases/100 person-years, respectively (P < 0.001). During early ART (first 4 months), adjusted TB rates among those with CD4 cell counts 0-200 cells/microl were 1.7-fold higher than during long-term ART (P = 0.026). Updated CD4 cell counts were the only patient characteristic independently associated with long-term TB risk.

CONCLUSION

Updated CD4 cell counts were the dominant predictor of TB risk during ART in this low-resource setting. Among those with baseline CD4 cell counts less than 200 cells/microl, the excess adjusted risk of TB during early ART was consistent with 'unmasking' of disease missed at baseline screening. TB incidence rates at CD4 cell counts of 200-500 cells/microl remained high and adjunctive interventions are required. TB prevention would be improved by ART policies that minimized the time patients spend with CD4 cell counts below a threshold of 500 cells/microl.