Background Despite negative baseline testing for tuberculosis (TB) with traditional (tuberculin skin test/TST, chest X-ray/CXR) or newer (interferon-gamma release assays/IGRAs) screening methods, a small number of patients receiving anti-tumor necrosis factor (TNF) therapies can develop TB during chronic treatment. The proportion of patients who display conversion of TB screening tests during therapy has not been adequately evaluated in prospective studies so far.
Objectives We aimed at studying prospectively the rate of TB test conversion (TST, IGRAs) during anti-TNF therapy in patients with negative baseline screening.
Methods Forty patients (mean age=46±14 years, females/males=23/17) with various rheumatic diseases (rheumatoid arthritis/RA =15, spondyloarthropathies/ SpA =24, other=1) and negative baseline TB screening (TST:<5 mm, negative T.Spot®-TB and QuantiFERON®-TB Gold In Tube/QFT-GIT, negative CXR) were included. A year after anti-TNFa therapy (adalimumab: n=16, infliximab: n=13, etanercept: n=10, certolizumab: n=1) all patients underwent re-testing with TST, both IGRAs and CXR.
Results Among the 40 patients enrolled, 13 patients (32.5%) demonstrated conversion of at least one screening assay. Fifteen percent showed conversion of TST (n=6), 10% of T.Spot®-TB (n=4) and 7.5% of QFT-GIT (n=3). Interestingly none of these patients showed concomitant conversion of ≥2 screening tests. No history of new M.Tb exposure or clinical and/or radiographic evidence of TB were noted. There were no significant difference in age, sex, disease diagnosis or duration, previous BCG vaccination, concomitant DMARD/steroid use or type of anti-TNFa treatment between those who converted (n=13) vs those who did not (n=27).
Conclusions These preliminary data suggest that approximately 1/3 of patients develop conversion of at least one screening assay for TB one year after anti-TNFa therapy. It remains unclear if these test conversions are due to new or past non-diagnosed (reconstitution of impaired immune response against M.Tb antigens) M. TB exposure. The clinical significance of these findings and the need for LTBI therapy in this group remains to be elucidated.
Disclosure of Interest None Declared