Performance of the QuantiFERON- TB gold test in children receiving immunosuppressive therapy for rheumatic diseases

Abstract

Objectives

The mainstay of treatment for pediatric rheumatological disease is disease-modifying anti-rheumatic agents which are immunosuppressive in nature and increase the susceptibility to tuberculosis. The aims and objectives were to evaluate the performance of the QuantiFERON®-TB Gold test (QFT) and Tuberculin skin test (TST) to diagnose latent tuberculosis in children receiving immunosuppressive therapy for rheumatic diseases in a tertiary hospital in South India.

Methods

This was a prospective observational study. 60 consecutive children diagnosed with various rheumatic diseases attending the Paediatric Rheumatology clinic on immunosuppressive therapy were included. The QFT and TST were performed on the same day. Data regarding the demography, diagnosis, treatment received and test results were collected and analysed.

Results

Among patients included (n = 60), two children had positive QFT and one child had positive TST. The agreement between tests was k = 0.85 and the proportion of latent tuberculosis was 5 %. All the children included were on conventional DMARDs and 3.3 % were on biological DMARDs. There was a significant decrease in the mitogen induced interferon level in children on treatment with hydroxychloroquine (p = 0.022) and a significant increase in the level in children on azathioprine (p = 0.006). Children on steroids had a lower range of mitogen-induced interferon levels.

Conclusion

QFT may be a more reliable test than TST for the detection of latent tuberculosis in children with rheumatic diseases receiving immunosuppressive treatment. The use of hydroxychloroquine and steroids might influence the mitogen-induced IFN-γ secretion and may interfere with the interpretation of the QFT test.