title: Utility of QuantiFERON-TB Gold In-Tube assay in adult, pulmonary and extrapulmonary, active tuberculosis diagnosis.
abstract: BACKGROUND
  Tuberculosis remains a public health problem in France and the diagnosis of tuberculosis disease (TB) is sometimes difficult. The aim of this study was to analyse the contribution of the QuantiFERON-TB Gold In-Tube assay (QFT-GIT) to TB diagnosis.
  
  
  METHODS
  Sixty patients hospitalized with TB, for whom a QFT-GIT assay had been performed between June 2008 and June 2011 at the University Hospital of Bondy in the north-east of Paris, were identified retrospectively. Clinical and laboratory data were collected. The sensitivity, specificity, predictive values, and likelihood ratios of the QFT-GIT were all calculated. Furthermore, the characteristics of patients testing positive were compared to those of patients testing negative, as well as the QFT-GIT values according to several different factors.
  
  
  RESULTS
  The sensitivity of the QFT-GIT was 85% (95% confidence interval (CI) 0.73-0.92) and specificity was 73.3% (95% CI 0.68-0.78). The positive predictive value was 39.5% and the negative predictive value was 97.3%. The positive and negative likelihood ratios were 3.2 and 0.20, respectively. The prevalence of TB in this population was 15% (pre-test probability). After a positive test result, the probability of TB increased to 40% (post-positive probability test); after a negative test result, it decreased to 4.5% (post-negative probability test). The combination of the QFT-GIT test with the tuberculin skin test brought no significant improvement in sensitivity. Factors significantly associated with a negative QFT-GIT result included older age, high C-reactive protein, a low lymphocyte count, and immunosuppressant intake. The test value in quantitative terms was significantly higher in those with lymph node TB than in those with pulmonary TB, and in younger patients (<40 years) than in older patients (>40 years old).
  
  
  CONCLUSIONS
  On its own, QFT-GIT is an insufficient tool to confirm the diagnosis of TB disease. However, it may form part of an ensemble of tools in combination with clinical, biological, and radiological assessments.
authors.affiliation: Service des Maladies Infectieuses et Tropicales, Hôpital Avicenne - Université Paris 13 Paris Cité Sorbonne, 125 route de Stalingrad, 93000 Bobigny, France. Electronic address: mohammed.azghay@avc.aphp.fr.
authors.forename: Mohammed
authors.initials: M
authors.lastname: Azghay
authors.affiliation: Service des Maladies Infectieuses et Tropicales, Hôpital Avicenne - Université Paris 13 Paris Cité Sorbonne, 125 route de Stalingrad, 93000 Bobigny, France.
authors.forename: Olivier
authors.initials: O
authors.lastname: Bouchaud
authors.affiliation: Service des Maladies Infectieuses et Tropicales, Hôpital Avicenne - Université Paris 13 Paris Cité Sorbonne, 125 route de Stalingrad, 93000 Bobigny, France.
authors.forename: Frederic
authors.initials: F
authors.lastname: Mechaï
authors.affiliation: Département d'Hématologie et Immunologie UF Autoimmunité et Hypersensibilités Hôpital Bichat Claude Bernard, Paris, France.
authors.forename: Pascale
authors.initials: P
authors.lastname: Nicaise
authors.affiliation: Service de Médecine Interne, Hôpital Saint Antoine, Paris, France.
authors.forename: Olivier
authors.initials: O
authors.lastname: Fain
authors.affiliation: Division of General Internal Medicine, Geneva University Hospital, Geneva, Switzerland.
authors.forename: Jérôme
authors.initials: J
authors.lastname: Stirnemann
mesh_terms: D000328:Adult; D002097:C-Reactive Protein; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005602:France; D006785:Hospitals, University; D006801:Humans; D007371:Interferon-gamma / Q000378:metabolism*; D008198:Lymph Nodes; D008297:Male; D008875:Middle Aged; D010297:Paris; D015995:Prevalence; D011336:Probability; D011933:Reagent Kits, Diagnostic; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D014374:Tuberculin Test; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis*
chemical_list: D011933:Reagent Kits, Diagnostic; D007371:Interferon-gamma; D002097:C-Reactive Protein
keywords: Diagnosis; IGRA; Interferon-gamma; QuantiFERON; Tuberculosis