title: Diagnostic Utility of New Equation for Active Tuberculosis Based on Parameters of Interferon-γ Release Assay.
abstract: BACKGROUND
  We derived a new equation to include interferon-γ (IFN-γ) levels in the QuantiFERON-Gold In-Tube (QFT-GIT) assay to discriminate active tuberculosis (ATB) infection from latent TB, and compared the diagnostic performance of the QFT-GIT assay and the new equation.
  
  
  METHODS
  From January 2013 through May 2015, we retrospectively enrolled 159 and 408 patients with and without ATB, respectively, in this study. Discriminant analysis was performed to derive an equation to distinguish the ATB group from the non-ATB group.
  
  
  RESULTS
  The sensitivity and specificity of the QFT-GIT assay for diagnosing ATB were 90.6% and 63.0%, respectively. The positive and negative predictive values of the QFT-GIT assay were 48.8% and 94.5%, respectively. When the optimal cutoff for the new equation [Z = (0.031 × Nil) + (0.007 × TBAg) - 0.978] was set to -0.435, the sensitivity and specificity were 84.3% and 69.1% (positive predictive value, 51.5%; negative predictive value, 91.9%), respectively.
  
  
  CONCLUSIONS
  The QFT-GIT assay and the equation derived from each IFN-γ could not discriminate ATB from latent TB without considering other cytokines involved in immunity against TB.
authors.affiliation: Department of Laboratory Medicine, School of Medicine, Kyung Hee University and Kyung Hee University Hospital at Gangdong, South Korea.
authors.forename: You La
authors.initials: Y
authors.lastname: Jeon
authors.affiliation: Department of Consumer Economics, Sookmyung Women's University, Seoul, South Korea.
authors.forename: Min-Jeong
authors.initials: MJ
authors.lastname: Kim
authors.affiliation: Department of Laboratory Medicine, School of Medicine, Kyung Hee University and Kyung Hee University Hospital at Gangdong, South Korea.
authors.forename: Woo-In
authors.initials: WI
authors.lastname: Lee
authors.affiliation: Department of Laboratory Medicine, School of Medicine, Kyung Hee University and Kyung Hee University Hospital at Gangdong, South Korea.
authors.forename: Myeong Hee
authors.initials: MH
authors.lastname: Kim
authors.affiliation: Department of Laboratory Medicine, School of Medicine, Kyung Hee University and Kyung Hee University Hospital at Gangdong, South Korea.
authors.forename: So Young
authors.initials: SY
authors.lastname: Kang
mesh_terms: D000328:Adult; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D059425:Interferon-gamma Release Tests / Q000379:methods*; D055985:Latent Tuberculosis / Q000175:diagnosis; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D014376:Tuberculosis / Q000175:diagnosis*
keywords: Nil ; QuantiFERON-Gold In-Tube assay (QFT-GIT); TBAg; active tuberculosis; interferon-γ; latent tuberculosis; release assay (IGRA)