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.