Incidence of tuberculosis in Korean patients with rheumatoid arthritis (RA): effects of RA itself and of tumor necrosis factor blockers

OBJECTIVE: To elucidate the incidence rate and relative risk of tuberculosis (TB) in patients with rheumatoid arthritis (RA) and in patients with RA treated with tumor-necrosis-factor (TNF) blockers in Korea. METHODS: Using data from the Korean National Tuberculosis Association (KNTA) as a control and data from a single-center cohort of patients with RA, we conducted an evaluation of 1285 patients with RA not exposed to TNF blockers and reviewed medical records of 90 and 103 patients with RA treated with infliximab and etanercept, respectively, between 2001 and 2005. RESULTS: The mean incidence rate of TB, reported by the KNTA, was 67.2 per 100,000 person years (PY) from 2001 to 2004. In the TNF-blocker-na?ve RA cohort, 9 cases of TB developed during 3497 PY of followup (257 per 100,000). In the infliximab-treated RA group, 2 cases of TB developed during 78.17 PY of followup (2558 per 100,000 PY), and there was no case of TB during 73.67 PY of followup in the etanercept-treated RA group. The risk of TB was higher in RA patients not treated with TNF blockers (sex- and age-adjusted risk ratio 8.9; 95% confidence interval 4.6-17.2), and in those treated with infliximab (sex- and age-adjusted risk ratio, 30.1; 95% confidence interval, 7.4-122.3) compared with the general Korean population. CONCLUSION: The risk of TB infection is 8.9-fold higher in Korean patients with RA and 30.1-fold higher in RA patients treated with infliximab, compared with the general Korean population.