Incidence of tuberculosis among korean patients with ankylosing spondylitis who are taking tumor necrosis factor blockers.

OBJECTIVE

To assess the incidence and relative risk of new tuberculosis (TB) infections in Korean patients with ankylosing spondylitis (AS) and patients with AS who are undergoing treatment with tumor necrosis factor (TNF) blockers.

METHODS

New cases of TB were identified by reviewing the medical records of 919 patients with AS not treated with TNF blockers and those of 354 patients with AS treated with adalimumab (n = 66), infliximab (n = 78), or etanercept (n = 210) between 2002 and 2009. Reference data were obtained from the Korean National Tuberculosis Association.

RESULTS

The mean incidence rate of TB was 69.8 per 100,000 person-years (PY) in the general population, 308 per 100,000 PY in the TNF blocker-naive AS cohort, and 561 per 100,000 PY in the TNF blocker-exposed AS cohort. The incidence rate of TB in the infliximab-treated AS cohort (540 per 100,000 PY) was higher than that in the adalimumab-treated AS cohort (490 per 100,000 PY). No cases of TB occurred in the etanercept-treated AS cohort. Comparing the relative risks of TB infections between the TNF blocker-exposed AS cohort and the TNF blocker-naive AS cohort, no statistically significant difference was identified (risk ratio 0.53; 95% CI 0.144-1.913).

CONCLUSION

The risk of TB was higher in the TNF blocker-naive AS cohort than it was in the general population. However, the risk of TB was not increased in the TNF blocker-exposed AS cohort compared with the TNF blocker-naive AS cohort. Among patients with AS, etanercept is associated with a lower risk of TB compared with monoclonal antibodies.