Performance of QuantiFERON®-TB Gold In-Tube assay in children receiving disease modifying anti-rheumatic drugs

Background: To evaluate the performance of the Quantiferon^®-TB Gold In-Tube (QFT-IT) interferon (IFN)-γ assay for the detection of latent tuberculosis infection (LTBI) in children receiving anti-rheumatic treatment in a tertiary referral hospital of Northern Greece. Methods: A total of 79 consecutive children receiving anti-rheumatic treatment [of which 18 screened prior to antitumor necrosis factor (TNF)-α treatment] were tested using Mantoux tuberculin skin test (TST) and QFT-IT. Association of both tests with risk factors for latent tuberculosis and Bacillus Calmette-Guerin immunization was determined. Influence of age, TNF-α inhibitors, systemic corticosteroids, conventional disease modifying anti-rheumatic drugs (DMARDs) and total duration of therapy on the QFT-IT mitogen-induced response was evaluated. Results: Agreement between TST and QFT-IT results was moderate (k=0.38). Frequency of QFT-IT indeterminate results was low (2.5%). In patients with risk factors for LTBI, the odds of a positive IFN-γ assay was increased by a factor of 27.6 (P=0.002), whereas there was no positive TST. There was a significant difference in the mitogen-induced IFN-γ secretion among various treatments (P=0.038). TNF-α inhibitors were associated with increased mitogen-induced IFN-γ secretion compared to monotherapy with conventional DMARDs (P=0.008). All children screened prior to anti-TNF-α treatment exhibited a negative QFT-IT and no active TB disease was detected during a 2-year follow-up. Conclusions: QFT-IT may be a more reliable test than TST for detection of LTBI in children with rheumatic diseases receiving anti-rheumatic treatment. Drug regimen might influence the mitogen-induced IFN-γ secretion and the effect of TNF-α inhibitors might vary according to the specific agent administered.