title: Risk factors associated with positive QuantiFERON-TB Gold In-Tube and tuberculin skin tests results in Zambia and South Africa.
abstract: BACKGROUND
  The utility of T-cell based interferon-gamma release assays for the diagnosis of latent tuberculosis infection remains unclear in settings with a high burden of tuberculosis.
  
  
  OBJECTIVE
  To determine risk factors associated with positive QuantiFERON-TB Gold In-Tube (QFT-GIT) and tuberculin skin test (TST) results and the level of agreement between the tests; to explore the hypotheses that positivity in QFT-GIT is more related to recent infection and less affected by HIV than the TST.
  
  
  METHODS
  Adult household contacts of tuberculosis patients were invited to participate in a cross-sectional study across 24 communities in Zambia and South Africa. HIV, QFT-GIT and TST tests were done. A questionnaire was used to assess risk factors.
  
  
  RESULTS
  A total of 2,220 contacts were seen. 1,803 individuals had interpretable results for both tests, 1,147 (63.6%) were QFT-GIT positive while 725 (40.2%) were TST positive. Agreement between the tests was low (kappa = 0.24). QFT-GIT and TST results were associated with increasing age (adjusted OR [aOR] for each 10 year increase for QFT-GIT 1.15; 95% CI: 1.06-1.25, and for TST aOR: 1.10; 95% CI 1.01-1.20). HIV positivity was less common among those with positive results on QFT-GIT (aOR: 0.51; 95% CI: 0.39-0.67) and TST (aOR: 0.61; 95% CI: 0.46-0.82). Smear positivity of the index case was associated with QFT-GIT (aOR: 1.25; 95% CI: 0.90-1.74) and TST (aOR: 1.39; 95% CI: 0.98-1.98) results. We found little evidence in our data to support our hypotheses.
  
  
  CONCLUSIONS
  QFT-GIT may not be more sensitive than the TST to detect risk factors associated with tuberculous infection. We found little evidence to support the hypotheses that positivity in QFT-GIT is more related to recent infection and less affected by HIV than the TST.
authors.affiliation: ZAMBART Project, University of Zambia, Lusaka, Zambia. kshanaube@zambart.org.zm
authors.forename: Kwame
authors.initials: K
authors.lastname: Shanaube
authors.forename: James
authors.initials: J
authors.lastname: Hargreaves
authors.forename: Katherine
authors.initials: K
authors.lastname: Fielding
authors.forename: Ab
authors.initials: A
authors.lastname: Schaap
authors.forename: Katherine-Anne
authors.initials: KA
authors.lastname: Lawrence
authors.forename: Bernadette
authors.initials: B
authors.lastname: Hensen
authors.forename: Charalambos
authors.initials: C
authors.lastname: Sismanidis
authors.forename: Angela
authors.initials: A
authors.lastname: Menezes
authors.forename: Nulda
authors.initials: N
authors.lastname: Beyers
authors.forename: Helen
authors.initials: H
authors.lastname: Ayles
authors.forename: Peter
authors.initials: P
authors.lastname: Godfrey-Faussett
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D003625:Data Collection; D005260:Female; D015658:HIV Infections / Q000175:diagnosis / Q000453:epidemiology; D006798:Housing; D006801:Humans; D007371:Interferon-gamma / Q000378:metabolism*; D055985:Latent Tuberculosis / Q000175:diagnosis* / Q000453:epidemiology* / Q000378:metabolism / Q000635:transmission; D008297:Male; D008875:Middle Aged; D009169:Mycobacterium tuberculosis / Q000472:pathogenicity; D012307:Risk Factors; D013019:South Africa; D014374:Tuberculin Test; D055815:Young Adult; D015024:Zambia
chemical_list: D007371:Interferon-gamma