title: Comparison of interferon-γ release assay to two cut-off points of tuberculin skin test to detect latent Mycobacterium tuberculosis infection in primary health care workers.
abstract: BACKGROUND
  An interferon-γ release assay, QuantiFERON-TB (QFT) test, has been introduced an alternative test for the diagnosis of latent Mycobacterium tuberculosis infection (LTBI). Here, we compared the performance of QFT with tuberculin skin test (TST) measured at two different cut-off points among primary health care work (HCW) in Brazil.
  
  
  METHODS
  A cross-sectional study was carried out among HCWs in four Brazilian cities with a known history of high incidence of TB. Results of the QFT were compared to TST results based on both ≥5 mm and ≥10 mm as cut-off points.
  
  
  RESULTS
  We enrolled 632 HCWs. When the cut-off value of ≥10 mm was used, agreement between QFT and TST was 69% (k = 0.31), and when the cut-off of ≥5 mm was chosen, the agreement was 57% (k = 0.22). We investigated possible factors of discordance of TST vs QFT. Compared to the TST-/QFT- group, risk factors for discordance in the TST+/QFT- group with TST cut-off of ≥5 mm included age between 41-45 years [OR = 2.70; CI 95%: 1.32-5.51] and 46-64 years [OR = 2.04; CI 95%: 1.05-3.93], BCG scar [OR = 2.72; CI 95%: 1.40-5.25], and having worked only in primary health care [OR = 2.30; CI 95%: 1.09-4.86]. On the other hand, for the cut-off of ≥10 mm, BCG scar [OR = 2.26; CI 95%: 1.03-4.91], being a household contact of a TB patient [OR = 1.72; CI 95%: 1.01-2.92] and having had a previous TST [OR = 1.66; CI 95%: 1.05-2.62], were significantly associated with the TST+/QFT- group. No statistically significant associations were found among the TST-/QFT+ discordant group with either TST cut-off value.
  
  
  CONCLUSIONS
  Although we identified BCG vaccination to contribute to the discordance at both TST cut-off measures, the current Brazilian recommendation for the initiation of LTBI treatment, based on information gathered from medical history, TST, chest radiograph and physical examination, should not be changed.
authors.affiliation: Laboratório de Epidemiologia of Universidade Federal do Espírito Santo, Vitória, Espírito Santo, Brazil; Núcleo de Doenças Infecciosas of Universidade Federal do Espírito Santo, Vitória, Espírito Santo, Brazil.
authors.forename: Fernanda Mattos
authors.initials: FM
authors.lastname: de Souza
authors.affiliation: Laboratório de Epidemiologia of Universidade Federal do Espírito Santo, Vitória, Espírito Santo, Brazil; Núcleo de Doenças Infecciosas of Universidade Federal do Espírito Santo, Vitória, Espírito Santo, Brazil.
authors.forename: Thiago Nascimento
authors.initials: TN
authors.lastname: do Prado
authors.affiliation: Coordenador do Núcleo de Controle da Tuberculose - Secretaria Municipal de Saúde - Manaus, Amazonas, Brazil.
authors.forename: Jair dos Santos
authors.initials: Jdos S
authors.lastname: Pinheiro
authors.affiliation: Laboratório de Epidemiologia of Universidade Federal do Espírito Santo, Vitória, Espírito Santo, Brazil; Núcleo de Doenças Infecciosas of Universidade Federal do Espírito Santo, Vitória, Espírito Santo, Brazil.
authors.forename: Renata Lyrio
authors.initials: RL
authors.lastname: Peres
authors.affiliation: Laboratório de Epidemiologia of Universidade Federal do Espírito Santo, Vitória, Espírito Santo, Brazil; Programa de Pós-graduação em Saúde Coletiva of Universidade Federal do Espírito Santo, Vitória, Espírito Santo, Brazil.
authors.forename: Thamy Carvalho
authors.initials: TC
authors.lastname: Lacerda
authors.affiliation: Laboratório de Epidemiologia of Universidade Federal do Espírito Santo, Vitória, Espírito Santo, Brazil; Departamento de Epidemiologia do Instituto de Medicina Social, Universidade Estadual do Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: Rafaela Borge
authors.initials: RB
authors.lastname: Loureiro
authors.affiliation: Programa de Controle de Tuberculose - Hospital Universitário Cassiano Antônio Moraes of Universidade Federal do Espírito Santo, Vitória, Espírito Santo, Brazil.
authors.forename: Jose Américo
authors.initials: JA
authors.lastname: Carvalho
authors.affiliation: Laboratório de Epidemiologia of Universidade Federal do Espírito Santo, Vitória, Espírito Santo, Brazil; Programa de Pós-graduação em Saúde Coletiva of Universidade Federal do Espírito Santo, Vitória, Espírito Santo, Brazil; Programa de Controle de Tuberculose - Hospital Universitário Cassiano Antônio Moraes of Universidade Federal do Espírito Santo, Vitória, Espírito Santo, Brazil.
authors.forename: Geisa
authors.initials: G
authors.lastname: Fregona
authors.affiliation: Laboratório de Epidemiologia of Universidade Federal do Espírito Santo, Vitória, Espírito Santo, Brazil; Estudantes de Graduação em Enfermagem e Obstetrícia da Universidade Federal do Espírito Santo, Vitória, Espírito Santo, Brazil.
authors.forename: Elias Santos
authors.initials: ES
authors.lastname: Dias
authors.affiliation: Laboratório de Epidemiologia of Universidade Federal do Espírito Santo, Vitória, Espírito Santo, Brazil; Estudantes de Graduação em Enfermagem e Obstetrícia da Universidade Federal do Espírito Santo, Vitória, Espírito Santo, Brazil.
authors.forename: Lorrayne Beliqui
authors.initials: LB
authors.lastname: Cosme
authors.affiliation: Núcleo de Doenças Infecciosas of Universidade Federal do Espírito Santo, Vitória, Espírito Santo, Brazil.
authors.forename: Rodrigo Ribeiro
authors.initials: RR
authors.lastname: Rodrigues
authors.affiliation: Division of Infectious Disease and Vaccinology, School of Public Health, University of California, Berkeley, California, United States of America.
authors.forename: Lee Wood
authors.initials: LW
authors.lastname: Riley
authors.affiliation: Laboratório de Epidemiologia of Universidade Federal do Espírito Santo, Vitória, Espírito Santo, Brazil; Programa de Pós-graduação em Saúde Coletiva of Universidade Federal do Espírito Santo, Vitória, Espírito Santo, Brazil.
authors.forename: Ethel Leonor Noia
authors.initials: EL
authors.lastname: Maciel
mesh_terms: D000328:Adult; D001500:BCG Vaccine / Q000008:administration & dosage; D001938:Brazil; D003430:Cross-Sectional Studies; D005260:Female; D006282:Health Personnel; D006801:Humans; D007371:Interferon-gamma / Q000032:analysis / Q000378:metabolism; D059425:Interferon-gamma Release Tests / Q000706:statistics & numerical data*; D055985:Latent Tuberculosis / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000276:immunology / Q000517:prevention & control; D008168:Lung / Q000000981:diagnostic imaging / Q000276:immunology / Q000382:microbiology; D008297:Male; D008875:Middle Aged; D009169:Mycobacterium tuberculosis / Q000276:immunology*; D011320:Primary Health Care; D011859:Radiography; D014374:Tuberculin Test / Q000706:statistics & numerical data*; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000276:immunology / Q000517:prevention & control; D014611:Vaccination
chemical_list: D001500:BCG Vaccine; D007371:Interferon-gamma