title: Effect of antiretroviral treatment on the risk of tuberculosis during South Africa's programme expansion.
abstract: OBJECTIVE
  The objective of this study is to estimate the effectiveness of antiretroviral treatment (ART) in preventing tuberculosis (TB) in HIV-infected people during the first 6 years of ART programme expansion.
  
  
  METHODS
  A cohort study comparing TB risk without ART and after ART initiation.
  
  
  METHODS
  Public sector HIV programme of the Free State province, South Africa.
  
  
  METHODS
  Seventy-four thousand and seventy-four HIV-infected people enrolled from 2004 until 2010, of whom 43 898 received ART and 30 176 did not.
  
  
  METHODS
  Combination ART.
  
  
  METHODS
  Time to first TB diagnosis, adjusted for CD4 cell count, weight, age, sex, previous TB, district and year, with ART, CD4 cell count and weight as time-varying covariates and with death as a competing risk.
  
  
  RESULTS
  Three thousand eight hundred and fifty-eight first TB episodes occurred during 78 202 person-years at risk with ART and 5669 episodes occurred during 62 801 person-years without ART [incidence rates 4.9 and 9.0 per 100 person-years, crude incidence rate ratio 0.55 (95% confidence interval 0.52-0.57)]. The adjusted subhazard ratio (SHR) of time to first TB episode after starting ART, compared with follow-up without ART, was 0.67 (0.64-0.70). Within CD4 cell count subgroups (<50, 50-199, 100-199, 200-349 and >350 cells/μl), the respective SHRs were 0.64 (0.57-0.71), 0.63 (0.57-0.70), 0.66 (0.61-0.72), 0.67 (0.62-0.72), 0.72 (0.63-0.83) and 0.97 (0.60-1.59). Adjusted SHRs for ART decreased with each year of enrolment, from 0.90 (0.77-1.04) in 2004 to 0.54 (0.43-0.67) in 2010.
  
  
  CONCLUSIONS
  ART was effective in preventing TB in HIV-infected patients with CD4 cell counts below 350 cells/μl, but less so than previously estimated. Effectiveness increased each year.
authors.affiliation: aNorwich Medical School, University of East Anglia, Norwich, UK bKnowledge Translation Unit, Lung Institute, Medical School, University of Cape Town, Cape Town, South Africa.
authors.forename: Max O
authors.initials: MO
authors.lastname: Bachmann
authors.forename: Venessa
authors.initials: V
authors.lastname: Timmerman
authors.forename: Lara R
authors.initials: LR
authors.lastname: Fairall
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D044966:Anti-Retroviral Agents / Q000627:therapeutic use*; D018791:CD4 Lymphocyte Count; D015331:Cohort Studies; D005260:Female; D015658:HIV Infections / Q000188:drug therapy* / Q000276:immunology; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D018570:Risk Assessment; D013019:South Africa; D014376:Tuberculosis / Q000453:epidemiology / Q000517:prevention & control*; D055815:Young Adult
chemical_list: D044966:Anti-Retroviral Agents