Smoking, BCG and employment and the risk of tuberculosis infection in HIV-infected persons in South Africa.
BACKGROUND
The increased susceptibility to latent tuberculosis infection (LTBI) of HIV-1-infected persons represents a challenge in TB epidemic control. However few studies have evaluated LTBI predictors in a generalized HIV/TB epidemic setting.


METHODS
The study recruited 335 HIV-infected participants from Khayelitsha, Cape Town between February 2008 and November 2010. Tuberculin skin tests and interferon-gamma release assays were performed on all participants and active TB excluded using a symptom screen, TB microscopy and culture.


RESULTS
LTBI prevalence was 52.7% and 61.2% (TST and IGRA respectively). Being a recent TB contact (OR 2.07; 95% C.I. 1.15-3.69) was associated with TST positivity. Participants with a CD4>200 had a two-fold higher risk of IGRA positivity compared to those with CD4 counts <200 (OR 2.07; 95% C.I. 0.99-4.34). There was also a 19% increase in IGRA positivity risk for every additional year of schooling and a strong association between years of schooling and employment (p = 0.0004). A decreased risk of IGRA positivity was observed in persons with a BCG scar (OR 0.46; 95% C.I. 0.31-0.69) and in smokers (OR 0.47; 95% C.I. 0.23-0.96).


CONCLUSIONS
We report the novel findings of a decreased risk of IGRA positivity in HIV-infected smokers possibly due to decreased interferon production, and in the persons with a BCG scar suggesting a protective role for BCG in this population. We also found an increased risk of TST positivity in employed persons, possibly due to ongoing transmission in public modes of transport.
Clinical Infectious Disease Research Initiative, Institute of Infectious Diseases and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, South Africa. tolullahoni@doctors.org.uk
Tolu
T
Oni
Hannah P
HP
Gideon
Nonzwakazi
N
Bangani
Relebohile
R
Tsekela
Ronnett
R
Seldon
Kathryn
K
Wood
Katalin A
KA
Wilkinson
Rene T
RT
Goliath
Tom H M
TH
Ottenhoff
Robert J
RJ
Wilkinson
D000328:Adult; D004651:Employment; D005260:Female; D015658:HIV Infections / Q000453:epidemiology* / Q000276:immunology; D006801:Humans; D059425:Interferon-gamma Release Tests; D008297:Male; D009163:Mycobacterium bovis / Q000276:immunology*; D012907:Smoking / Q000009:adverse effects*; D013019:South Africa / Q000453:epidemiology; D014374:Tuberculin Test; D014376:Tuberculosis / Q000453:epidemiology* / Q000276:immunology