title: Disease activity is an important factor for indeterminate interferon-γ release assay results in children with inflammatory bowel disease.
abstract: BACKGROUND
  Interferon-γ release assay (IGRA) is widely used for screening of latent tuberculosis (TB) before and during biological therapy (BT). An indeterminate result of IGRA represents a limitation in the management of inflammatory bowel disease (IBD). Data on factors influencing IGRA results are scarce in children. The aim of the study was to identify factors influencing IGRA results in children with IBD.
  
  
  METHODS
  Seventy-two children with IBD (59 Crohn disease, 11 ulcerative colitis, 2 IBD-unclassified) indicated for BT were tested for TB infection (history, TB skin test, chest radiograph, IGRA; QuantiFERON-TB Gold in tube [QFT]) and consecutively retested using QFT in 1-year intervals.
  
  
  RESULTS
  We recorded 165 results of QFT (3% positive, 87% negative, and 10% indeterminate results). During follow-up we identified 4 conversions of negative QFT to positivity (3%) and 4 reversions (4%). Patients with indeterminate results of QFT had significantly lower actual weight-for-height z score (P = 0.022), higher platelet count (P = 0.00017), and lower levels of serum albumin (P = 0.015) compared with patients with positive or negative QFT. Indeterminate QFT was associated with corticosteroid treatment, BT, and disease activity, but not with treatment by immunomodulators. In a subanalysis of patients with Crohn disease alone, Pediatric Crohn's Disease Activity Index was identified as single independent risk factor for indeterminate results (P = 0.00037).
  
  
  CONCLUSIONS
  Although corticosteroid treatment is traditionally considered to be the main risk factor for indeterminate results of IGRA, the disease activity of IBD has even more profound effects on the results.
authors.affiliation: *Department of Pediatrics, University Hospital Motol and Second Faculty of Medicine, Charles University in Prague †National Reference Laboratory for Mycobacteria, National Institute of Public Health ‡Department of Clinical Microbiology, Na Bulovce Hospital, Prague, Czech Republic.
authors.forename: Ondrej
authors.initials: O
authors.lastname: Hradsky
authors.forename: Jan
authors.initials: J
authors.lastname: Ohem
authors.forename: Kristyna
authors.initials: K
authors.lastname: Zarubova
authors.forename: Katarina
authors.initials: K
authors.lastname: Mitrova
authors.forename: Marianna
authors.initials: M
authors.lastname: Durilova
authors.forename: Radana
authors.initials: R
authors.lastname: Kotalova
authors.forename: Jiri
authors.initials: J
authors.lastname: Nevoral
authors.forename: Ilona
authors.initials: I
authors.lastname: Zemanova
authors.forename: Pavel
authors.initials: P
authors.lastname: Dryak
authors.forename: Jiri
authors.initials: J
authors.lastname: Bronsky
mesh_terms: D000293:Adolescent; D000305:Adrenal Cortex Hormones / Q000009:adverse effects / Q000627:therapeutic use; D001835:Body Weight; D002648:Child; D003093:Colitis, Ulcerative / Q000150:complications / Q000473:pathology; D003424:Crohn Disease / Q000150:complications / Q000473:pathology; D005260:Female; D006801:Humans; D015212:Inflammatory Bowel Diseases / Q000150:complications* / Q000473:pathology; D007371:Interferon-gamma / Q000378:metabolism*; D059425:Interferon-gamma Release Tests; D055985:Latent Tuberculosis / Q000150:complications / Q000175:diagnosis* / Q000378:metabolism; D008297:Male; D010976:Platelet Count; D012307:Risk Factors; D012709:Serum Albumin / Q000378:metabolism; D014374:Tuberculin Test
chemical_list: D000305:Adrenal Cortex Hormones; D012709:Serum Albumin; D007371:Interferon-gamma