title: Longitudinal analysis of QuantiFERON-TB Gold In-Tube in children with adult household tuberculosis contact in South Africa: a prospective cohort study.
abstract: BACKGROUND
  QuantiFERON-TB Gold In Tube (QFT-GIT) is a tool for detecting M. tuberculosis infection. However, interpretation and utility of serial QFT-GIT testing of pediatric tuberculosis (TB) contacts is not well understood. We compared TB prevalence between baseline and 6 months follow-up using QFT-GIT and tuberculin skin testing (TST) in children who were household contacts of adults with pulmonary TB in South Africa, and explored factors associated with QFT-GIT conversions and reversions.
  
  
  METHODS
  Prospective study with six month longitudinal follow-up.
  
  
  RESULTS
  Among 270 enrolled pediatric contacts, 196 (73%) underwent 6-month follow-up testing. The 6-month prevalence estimate of MTB infection in pediatric contacts increased significantly from a baseline of 29% (79/270, 95%CI [24-35]) to 38% (103/270, 95% CI [32-44], p<0.001) using QFT-GIT; prevalence increased from a baseline of 28% (71/254, 95%CI [23-34]) to 33% (88/263, 95%CI [21-32], p = 0.002) using TST. Prevalence estimates were influenced by thresholds for positivity for TST, but not for QFT-GIT. Among 134 children with a negative or indeterminate baseline QFT-GIT, 24 (18%) converted to positive at follow-up; conversion rates did not differ significantly when using more stringent thresholds to define QFT-GIT conversion. Older age >10 years (AOR 8.9 95%CI [1.1-72]) and baseline TST positivity ≥5 mm (AOR 5.2 95%CI [1.2-23]) were associated with QFT-GIT conversion. Among 62 children with a positive baseline QFT-GIT, 9 (15%) reverted to negative; female gender (AOR 18.5 95%CI [1.1-321]; p = 0.04] was associated with reversion, while children with baseline positive TST were less likely to have QFT-GIT reversion (AOR 0.01 95%CI [0.001-0.24]).
  
  
  CONCLUSIONS
  Among pediatric contacts of adult household TB cases in South Africa, prevalence estimates of TB infection increased significantly from baseline to 6 months. Conversions and reversions occurred among pediatric TB contacts using QFT-GIT, but QFT-GIT conversion rates were less influenced by thresholds used for conversions than were TST conversion rates.
authors: Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America. mshah28@jhmi.edu
authors: Maunank
authors: M
authors: Shah
authors: Tafadzwa S
authors: TS
authors: Kasambira
authors: Peter V
authors: PV
authors: Adrian
authors: Shabir A
authors: SA
authors: Madhi
authors: Neil A
authors: NA
authors: Martinson
authors: Susan E
authors: SE
authors: Dorman
mesh_terms: D000328:Adult; D002648:Child; D002675:Child, Preschool; D003955:Diagnostic Tests, Routine / Q000379:methods*; D005191:Family Characteristics; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D008297:Male; D015995:Prevalence; D011446:Prospective Studies; D011933:Reagent Kits, Diagnostic; D013019:South Africa / Q000453:epidemiology; D014374:Tuberculin Test; D014376:Tuberculosis / Q000175:diagnosis* / Q000453:epidemiology
chemical_list: D011933:Reagent Kits, Diagnostic