To characterize the pattern of positive conversion of interferon gamma release assay (IGRA) in patients with Crohn's disease (CD) during infliximab therapy in China, which has a high burden of tuberculosis.
Eligible patients with CD who received serial IGRA screening during infliximab therapy from January 2015 to March 2020 were retrospectively included. The positive conversion rate of IGRA and the risk of subsequent tuberculosis of the patients were analyzed.
A total of 128 patients with CD were included, and the median time from the initiation of IFX treatment to positive conversion or the last follow-up test of IGRA was 43.6 weeks. At baseline 3.9% of the patients were positive for IGRA and received prophylactic anti-tuberculosis treatment. In the other 123 patients with negative IGRA at baseline, 6.5% had IGRA positive conversion during infliximab treatment, and one (12.5%) who was exposed to Mycobacterium tuberculosis was diagnosed as having active tuberculosis. The conversion rate at 40 weeks, 2 years and 3 years after treatment were 10.0% (6/60), 2.2% (1/46) and 5.9% (1/17), respectively. Age, sex, history of smoking and alcohol consumption, disease severity (Crohn's disease activity index score) and immunosuppressive therapy were not significantly associated with latent tuberculosis test conversion.
Positive conversion of IGRA occurs early during treatment with infliximab for CD and the monitoring frequency of IGRA should be appropriately increased at the early stage of treatment. Physicians should pay attention to patient's history of tuberculosis exposure and carry out surveillance in a timely fashion.