Clinical characteristics of anti-TNF α agents-related tuberculosis in ankylosing spondylitis compared with rheumatoid arthritis

Abstract

Introduction: Ankylosing spondylitis (AS) is a rheumatic disease for which anti-TNF α agents are effective. Tuberculosis (TB) is one of the serious infectious complications of anti-TNF α agents. However, the clinical characteristics of anti-TNF α agents-related TB in AS are not well described. The objective of this thesis was to investigate the clinical characteristics of active TB in AS patients after anti-TNF α agents are prescribed. Methods: All patients with AS or rheumatoid arthritis (RA) who took anti-TNF α agents were enrolled at Seoul National University Hospital between Jan 2001 and Aug 2011. The medical records were reviewed for all the patients. TB was defined as the presence of M. tuberculosis in culture and/or typical radiographic findings and/or clinical response to anti-TB medication. The clinical characteristics of AS patients who developed TB were compared with those of RA. Results: Fourteen cases of TB were reported (AS, 7 out of 404 anti-TNF α agent treatment episodes

RA, 7 out of 277). The incidence rate of TB in AS for the anti-TNF α agent treated patients (600.2 per 100,000 person years) (95% CI 241.3-1236.3) was comparable with that of RA (771.6 per 100,000 person years) (95% CI 310.2-1589.9). Patients with AS and TB were younger with a significantly lower body mass index (BMI) than that of RA (19.9 ±2.6 vs 23.9 ±3.3, p= 0.027). In the multivariate analysis, a low BMI (OR 13.3, p=0.018, age and sex adjusted) was a significant risk factor for TB in the AS group. The time to TB in AS was longer than in RA (19.4 months vs 7.0 months, p=0.409). The proportion of extrapulmonary disease was similar for both groups (85.7% vs 85.7%). Prevalence of latent TB infection was estimated to be 31.1% vs 25.7% in the cohort of AS and RA patients, respectively. All 3 cases that developed TB despite treatment for latent TB were AS patients. Conclusions: When anti-TNF α agents are prescribed in AS, TB can develop as frequently as in RA. TB manifests later in AS than in RA by 1 year after initiation of anti-TNF α agents. Extrapulmonary TB was as prevalent as in RA. Cautious use of anti-TNF α agents with close surveillance for TB development should be exercised for a minimum of 1.5 years in AS.