Background: This study compared the performance of 2 interferon-γ release assays (IGRAs) and conventional screening tests in patients with inflammatory arthritis undergoing screening for latent tuberculosis infection (LTBI) before treatment with anti-TNFα compounds.
Methods: Successive patients were subjected to conventional LTBI screening, including a tuberculin skin test (TST). The T-SPOT.TB test was performed on all patients and the QuantiFERON-TB Gold test was performed on a large subset. The results of the IGRAs were compared to the results of conventional screening tests.
Results: A total 150 patients were evaluated. The majority (57.9%) had rheumatoid arthritis (RA). Previous vaccination with Bacille Calmette-Guerin was confirmed in 82% of patients. No patient had received prior anti-TB treatment. A total 57 patients (38.0%) had at least one positive conventional risk factor. In contrast, an unequivocally positive T-SPOT.TB test was observed in only 14 (9.8%). There was 98.2% agreement between the two IGRAs. Statistically significant associations were observed between each of the IGRAs and both TST and risk history, but not CXR. A positive IGRA result was significantly associated with increased age. No patient developed reactivation of TB during the follow-up period.
Interpretation: This study provides compelling evidence to suggest that IGRAs may have utility when screening for LTBI before anti-TNFα therapy in patients with immune-mediated inflammatory diseases. The observations reported here also highlight the inadequate performance of CXR as a marker of LTBI.
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