title: Mycobacterium tuberculosis infection in young children: analyzing the performance of the diagnostic tests.
abstract: OBJECTIVE
  This study evaluated the performance of the Tuberculin Skin Test (TST) and Quantiferon-TB Gold in-Tube (QFT) and the possible association of factors which may modify their results in young children (0-6 years) with recent contact with an index tuberculosis case.
  
  
  METHODS
  A cross-sectional study including 135 children was conducted in Manaus, Amazonas-Brazil. The TST and QFT were performed and the tests results were analyzed in relation to the personal characteristics of the children studied and their relationship with the index case.
  
  
  RESULTS
  The rates of positivity were 34.8% (TST) and 26.7% (QFT), with 14.1% of indeterminations by the QFT. Concordance between tests was fair (Kappa = 0.35 P<0.001). Both the TST and QFT were associated with the intensity of exposure (Linear OR = 1.286, P = 0.005; Linear OR = 1.161, P = 0.035 respectively) with only the TST being associated with the time of exposure (Linear OR = 1.149, P = 0.009). The presence of intestinal helminths in the TST+ group was associated with negative QFT results (OR = 0.064, P = 0.049). In the TST- group lower levels of ferritin were associated with QFT+ results (Linear OR = 0.956, P = 0.036).
  
  
  CONCLUSIONS
  Concordance between the TST and QFT was lower than expected. The factors associated with the discordant results were intestinal helminths, ferritin levels and exposure time to the index tuberculosis case. In TST+ group, helminths were associated with negative QFT results suggesting impaired cell-mediated immunity. The TST-&QFT+ group had a shorter exposure time and lower ferritin levels, suggesting that QFT is faster and ferritin may be a potential biomarker of early stages of tuberculosis infection.
authors.affiliation: Pós-Graduação em Medicina Tropical, Universidade do Estado do Amazonas/Fundação de Medicina Tropical Dr. Heitor Vieira Dourado, Manaus, Amazonas, Brazil; Departament de Salut Pública, Facultat de Medicina, Universitat de Barcelona, Barcelona, Catalunya, Spain; Servei de Pediatria, CAP Valldoreix, Unitat de Investigació Fundació Mútua Terrassa, Hospital Universitari Mútua Terrassa, Terrassa, Catalunya, Spain.
authors.forename: Tomàs M
authors.initials: TM
authors.lastname: Pérez-Porcuna
authors.affiliation: Departament de Salut Pública, Facultat de Medicina, Universitat de Barcelona, Barcelona, Catalunya, Spain; Institut d'Investigacions Biomèdiques August Pi i Sunyer, Barcelona, Catalunya, Spain.
authors.forename: Carlos
authors.initials: C
authors.lastname: Ascaso
authors.affiliation: Laboratório de Imunologia Básica e Aplicada, Fundação de Hematologia e Hemoterapia do Amazonas, Manaus, Amazonas, Brazil; Universidade Federal do Amazonas. Manaus, Amazonas, Brazil.
authors.forename: Adriana
authors.initials: A
authors.lastname: Malheiro
authors.affiliation: Departament de Salut Pública, Facultat de Medicina, Universitat de Barcelona, Barcelona, Catalunya, Spain.
authors.forename: Rosa
authors.initials: R
authors.lastname: Abellana
authors.affiliation: Fundação de Medicina Tropical Dr. Heitor Vieira Dourado, Manaus, Amazonas, Brazil.
authors.forename: Marilaine
authors.initials: M
authors.lastname: Martins
authors.affiliation: Fundação de Medicina Tropical Dr. Heitor Vieira Dourado, Manaus, Amazonas, Brazil.
authors.forename: José Felipe Jardim
authors.initials: JF
authors.lastname: Sardinha
authors.affiliation: Pós-Graduação em Medicina Tropical, Universidade do Estado do Amazonas/Fundação de Medicina Tropical Dr. Heitor Vieira Dourado, Manaus, Amazonas, Brazil.
authors.forename: Patricia
authors.initials: P
authors.lastname: Quincó
authors.affiliation: Centro de Referência da Tuberculose, Policlínica Cardoso Fontes, Manaus, Amazonas, Brazil.
authors.forename: Irineide Assumpção
authors.initials: IA
authors.lastname: Antunes
authors.affiliation: Pós-Graduação em Medicina Tropical, Universidade do Estado do Amazonas/Fundação de Medicina Tropical Dr. Heitor Vieira Dourado, Manaus, Amazonas, Brazil; Programa de Controle da Tuberculose, Departamento de Vigilância Epidemiológica, Fundação de Vigilância em Saúde do Estado do Amazonas, Manaus, Amazonas, Brazil.
authors.forename: Marlucia
authors.initials: M
authors.lastname: da Silva Garrido
authors.affiliation: Pós-Graduação em Medicina Tropical, Universidade do Estado do Amazonas/Fundação de Medicina Tropical Dr. Heitor Vieira Dourado, Manaus, Amazonas, Brazil; Instituto de Patologia Tropical e Saúde Pública, Universidade Federal de Goiás, Goiânia, Goiás, Brazil.
authors.forename: Samira
authors.initials: S
authors.lastname: Bührer-Sékula
authors.affiliation: Pós-Graduação em Medicina Tropical, Universidade do Estado do Amazonas/Fundação de Medicina Tropical Dr. Heitor Vieira Dourado, Manaus, Amazonas, Brazil; Instituto Leônidas e Maria Deane - Fiocruz Amazônia, Fundação Oswaldo Cruz, Manaus, Amazonas, Brazil.
authors.forename: Flor Ernestina
authors.initials: FE
authors.lastname: Martinez-Espinosa
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007371:Interferon-gamma / Q000378:metabolism; D008297:Male; D009163:Mycobacterium bovis / Q000276:immunology; D009169:Mycobacterium tuberculosis / Q000502:physiology*; D014374:Tuberculin Test; D014376:Tuberculosis / Q000175:diagnosis* / Q000378:metabolism / Q000517:prevention & control; D014611:Vaccination
chemical_list: D007371:Interferon-gamma