Risk factors associated with indeterminate gamma interferon responses in the assessment of latent tuberculosis infection in a high-incidence environment.
The performance of gamma interferon (IFN-γ) release assays (IGRA) in the detection of latent tuberculosis (TB) infection is limited by the higher rates of indeterminate results in HIV-infected persons, who bear the brunt of TB disease in some high-burden settings. The objective of the study was to evaluate predictors of indeterminate IGRA results in the overall study population and in HIV-infected persons. The study setting is Khayelitsha, an informal township in the Western Cape of South Africa, with a high burden of TB and HIV infection. A total of 561 asymptomatic persons were recruited from the day hospital and youth centers. A questionnaire was used to collect demographic information, and blood tests, including CD4 counting and a 7-day in-house IGRA, were performed. The overall prevalence of indeterminate IGRA results was 8.6% (48/561), and this was higher in HIV-infected than in HIV-uninfected persons (11.5% [38/330] versus 4.3% [10/231], respectively; P = 0.003). In the overall study population, predictors of indeterminate IGRA results were the presence of HIV infection (odds ratio [OR], 2.36; 95% confidence interval [CI], 1.10 to 5.08) and the presence of a Mycobacterium bovis BCG scar (OR, 2.48; 95% CI, 1.23 to 5.01). Long-term township residents were significantly less likely to have indeterminate results than recent migrants (OR, 0.30; 95% CI, 0.11 to 0.80). Among HIV-infected persons, participants with CD4 counts of >200 cells/mm(3) and long-term residents were significantly less likely to have indeterminate IGRA results (OR of 0.21 with a 95% CI of 0.09 to 0.48 and OR of 0.22 with a 95% CI of 0.07 to 0.68, respectively). We evaluated risk factors for indeterminate IGRA results and report a higher rate of indeterminate results among HIV-infected persons, particularly those with lower CD4 counts. Of note, a recent move to the township was associated with a higher risk of indeterminate IGRA results.
Clinical Infectious Diseases Research Initiative, Institute of Infectious Diseases and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, 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; D018791:CD4 Lymphocyte Count; D005260:Female; D015658:HIV Infections / Q000150:complications* / Q000276:immunology*; D006801:Humans; D059425:Interferon-gamma Release Tests / Q000379:methods*; D055985:Latent Tuberculosis / Q000175:diagnosis*; D008297:Male; D012680:Sensitivity and Specificity; D013019:South Africa; D011795:Surveys and Questionnaires