title: Agreement between QuantiFERON®-TB Gold In-Tube and the tuberculin skin test and predictors of positive test results in Warao Amerindian pediatric tuberculosis contacts.
abstract: BACKGROUND
  Interferon-gamma release assays have emerged as a more specific alternative to the tuberculin skin test (TST) for detection of tuberculosis (TB) infection, especially in Bacille Calmette-Guérin (BCG) vaccinated people. We determined the prevalence of Mycobacterium tuberculosis infection by TST and QuantiFERON®-TB Gold In-Tube (QFT-GIT) and assessed agreement between the two test methods and factors associated with positivity in either test in Warao Amerindian children in Venezuela. Furthermore, progression to active TB disease was evaluated for up to 12 months.
  
  
  METHODS
  163 HIV-negative childhood household contacts under 16 years of age were enrolled for TST, QFT-GIT and chest X-ray (CXR). Follow-up was performed at six and 12 months. Factors associated with TST and QFT-GIT positivity were studied using generalized estimation equations logistic regression models.
  
  
  RESULTS
  At baseline, the proportion of TST positive children was similar to the proportion of children with a positive QFT-GIT (47% vs. 42%, p = 0.12). Overall concordance between QFT-GIT and TST was substantial (kappa 0.76, 95% CI 0.46-1.06). Previous BCG vaccination was not associated with significantly increased positivity in either test (OR 0.68, 95% CI 0.32-1.5 for TST and OR 0.51, 95% CI 0.14-1.9 for QFT-GIT). Eleven children were diagnosed with active TB at baseline. QFT-GIT had a higher sensitivity for active TB (88%, 95% CI 47-98%) than TST (55%, 95% CI 24-83%) while specificities were similar (respectively 58% and 55%). Five initially asymptomatic childhood contacts progressed to active TB disease during follow-up.
  
  
  CONCLUSIONS
  Replacement of TST by the QFT-GIT for detection of M. tuberculosis infection is not recommended in this resource-constrained setting as test results showed substantial concordance and TST positivity was not affected by previous BCG vaccination. The QFT-GIT had a higher sensitivity than the TST for the detection of TB disease. However, the value of the QFT-GIT as an adjunct in diagnosing TB disease is limited by a high variability in QFT-GIT results over time.
authors.affiliation: Laboratorio de Tuberculosis, Instituto de Biomedicina, Universidad Central de Venezuela, Caracas, Venezuela. lillyverhagen@hotmail.com.
authors.forename: Lilly M
authors.initials: LM
authors.lastname: Verhagen
authors.forename: Mailis
authors.initials: M
authors.lastname: Maes
authors.forename: Julian A
authors.initials: JA
authors.lastname: Villalba
authors.forename: Adriana
authors.initials: A
authors.lastname: d'Alessandro
authors.forename: Lazaro Perez
authors.initials: LP
authors.lastname: Rodriguez
authors.forename: Mercedes F
authors.initials: MF
authors.lastname: España
authors.forename: Peter W M
authors.initials: PW
authors.lastname: Hermans
authors.forename: Jacobus H
authors.initials: JH
authors.lastname: de Waard
mesh_terms: D000293:Adolescent; D002648:Child; D002669:Child Welfare; D002675:Child, Preschool; D016358:Contact Tracing; D005260:Female; D006801:Humans; D007223:Infant; D059425:Interferon-gamma Release Tests / Q000379:methods*; D008297:Male; D009169:Mycobacterium tuberculosis; D044382:Population Groups / Q000706:statistics & numerical data; D011237:Predictive Value of Tests; D011933:Reagent Kits, Diagnostic; D014374:Tuberculin Test / Q000379:methods*; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis* / Q000453:epidemiology; D014687:Venezuela
chemical_list: D011933:Reagent Kits, Diagnostic