Tuberculin skin test repetition after TNF-α inhibitors in patients with chronic inflammatory arthritis: a long-term retrospective cohort in endemic area.

Objectives: To evaluate the tuberculin skin test (TST) conversion in chronic inflammatory arthropathies (CIA) patients on TNFα inhibitors (TNFi) and without previous latent tuberculosis infection (LTBI) treatment.

Methods: Patients with rheumatoid arthritis (RA), ankylosing spondylitis (AS) and psoriatic arthritis (PsA) with negative LTBI were retrospectively evaluated for TST conversion and active tuberculosis (TB) after six months of exposition to TNFi. Two groups were compared: patients who repeated TST (TST-repetition) during the follow-up and patients who did not (non-TST-repetition).

Results: A total of 355 CIA patients on TNFi were screened and 138 (38.9%) did not fulfill the inclusion criteria. Of the remaining 217 CIA patients, 81 (37.3%) repeated TST during TNFi treatment. TST conversion rate was observed in 18 (22.2%) patients without significant differences among CIA (p = 0.578). The number of TB cases was low (n = 10; 4.6%) and was similar in TST-repetition and non-TST-repetition groups [2 (2.5%) vs. 8 (5.9%), p = 0.328]. Of note, 30% of active TB occurred early (6-12 months of TNFi exposure) and the median (full range) time to incident TB was 1.3 (0.6-10.6) years, whereas the median (full range) time to TST repetition was later [3.3 (0.5-13.4) years]. The incidence of active TB was lower among RA patients than AS patients [342 (95% CI 41 - 1446) vs. 1.454 (95% CI 594-2993)/100,000 patient-years, p = 0.049].

Conclusion: These results indicate that TST repetition is associated with a high conversion rate, suggesting the need for recommended treatment. The delayed repetition of TST and low number of active TB cases hampered the evaluation of this strategy effectiveness to prevent active infection. Larger studies with systematic repetition patterns are necessary. In addition, the study highlights the need for a greater surveillance for TB in AS patients.