Comparison of tuberculosis incidence in ankylosing spondylitis and rheumatoid arthritis during tumor necrosis factor inhibitor treatment in an intermediate burden area.

Clinical characteristics of antitumor necrosis factor (TNF) agents-related tuberculosis (TB) in ankylosing spondylitis (AS) are not well described. The aim was to compare the incidences and the characteristics of TB in AS and rheumatoid arthritis (RA) during TNF inhibitor treatment. AS (n = 1,322) and RA (n = 3,154) patients who received medical care between January 2001 and August 2011 were enrolled. The incidence of TB in patients treated, or not, with TNF inhibitors and the clinical features associated with TB were explored. Seven patients with AS and seven with RA developed TB while receiving TNF inhibitor therapy, resulting in an incidence rate of 600.2/100,000 person-years (PYs) (95 % confidence interval (CI), 241.3-1236.3) for those with AS and 771.6/100,000 PYs (95 % CI, 310.2-1589.9) for those with RA. Incidence rate ratios for TNF inhibitor-treated vs. untreated patients were 4.87 for AS (95 % CI, 1.50-15.39; p < 0.001) and 3.61 for RA (95 % CI, 1.38-8.07; p < 0.001). Low body mass index was identified as a significant risk factor for TB in the AS group (odds ratio (OR), 13.0; p = 0.002). Extrapulmonary TB was predominant at 85.7 % during TNF inhibitor treatment. Three (42.8 %) of the AS patients, but none of the RA patients, developed TB with concomitant isoniazid. All AS patients recovered from TB whereas two of seven RA patients died. Treatment with TNF inhibitors significantly increases the risk of extrapulmonary TB in AS. Symptoms of infection should warrant clinicians to evaluate for TB during TNF inhibitor therapy in AS patients.