title: A comparison of interferon-γ and IP-10 for the diagnosis of tuberculosis.
abstract: OBJECTIVE
  Interferon-γ and IP-10 release assays are diagnostic tests for tuberculosis infection. We have compared the accuracy of IP-10 and QuantiFERON-TB Gold In-tube [QFT-IT] in Tanzanian children suspected of having active tuberculosis (TB).
  
  
  METHODS
  Hospitalized Tanzanian children with symptoms of TB were tested with the QFT-IT and IP-10 tests and retrospectively classified into diagnostic groups. Adults with confirmed TB were assessed in parallel.
  
  
  RESULTS
  A total of 203 children were included. The median age was 3.0 years (interquartile range: 1.2-7.0), 38% were HIV infected, 36% were aged <2 years, and 58% had a low weight-for-age. IP-10 and QFT-IT test performance was comparable but sensitivity was low: 33% (1 of 3) in children with confirmed TB and 29% (8 of 28) in children with probable TB. Rates of indeterminate responders were high: 29% (59 of 203) for IP-10 and 26% (53 of 203) for QFT-IT. Age <2 years was associated with indeterminate test outcome for both IP-10 (adjusted odds ratio [aOR]: 2.2; P = .02) and QFT-IT (aOR: 2.4; P = .01). TB exposure was associated with positive IP-10 test outcome (aOR: 3.6; P = .01) but not with positive QFT-IT outcome (aOR 1.4; P = .52). In 102 adults, test sensitivity was 80% for both tests (P = .248).
  
  
  CONCLUSIONS
  Although IP-10 and QFT-IT performed well in Tanzanian adults, the tests exhibited an equally poor performance in diagnosing active TB in children. Test performance was especially compromised in young children. Neither test can be recommended for use in hospitalized children in high-burden settings.
authors.affiliation: Clinical Research Centre, and Departments of Paediatrics and line.lindebo.holm@gmail.com.
authors.forename: Line Lindebo
authors.initials: LL
authors.lastname: Holm
authors.affiliation: Infectious Diseases, Copenhagen University Hospital Hvidovre, Hvidovre, Denmark;
authors.forename: Michala Vaaben
authors.initials: MV
authors.lastname: Rose
authors.affiliation: Muhimbili Medical Research Centre, National Institute for Medical Research, Dar es Salaam, Tanzania;
authors.forename: Godfather
authors.initials: G
authors.lastname: Kimaro
authors.affiliation: Department of International Health, Immunology and Microbiology, University of Copenhagen, Copenhagen, Denmark;
authors.forename: Ib C
authors.initials: IC
authors.lastname: Bygbjerg
authors.affiliation: Muhimbili Medical Research Centre, National Institute for Medical Research, Dar es Salaam, Tanzania;
authors.forename: Sayoki G
authors.initials: SG
authors.lastname: Mfinanga
authors.affiliation: Clinical Research Centre, and Department for Pulmonary and Infectious Diseases, Nordsjaelland Hospital, Hillerød, Denmark; and.
authors.forename: Pernille
authors.initials: P
authors.lastname: Ravn
authors.affiliation: Department of Infectious Disease Immunology, Statens Serum Institute, Copenhagen, Denmark.
authors.forename: Morten
authors.initials: M
authors.lastname: Ruhwald
mesh_terms: D054357:Chemokine CXCL10 / Q000097:blood*; D002648:Child; D002675:Child, Preschool; D003906:Developing Countries; D005260:Female; D015658:HIV Infections / Q000097:blood / Q000175:diagnosis; D006801:Humans; D007223:Infant; D007371:Interferon-gamma / Q000097:blood*; D059425:Interferon-gamma Release Tests; D008297:Male; D009894:Opportunistic Infections / Q000097:blood / Q000175:diagnosis; D011237:Predictive Value of Tests; D013636:Tanzania; D014376:Tuberculosis / Q000175:diagnosis*
chemical_list: C114753:CXCL10 protein, human; D054357:Chemokine CXCL10; D007371:Interferon-gamma
keywords: IP-10; children; diagnosis; interferon-γ release assay; tuberculosis