Non-steroidal anti-inflammatory drugs in patients with stable ankylosing spondylitis receiving tumor necrosis factor inhibitor: continued vs withdrawn

To investigate the effect of non-steroidal anti-inflammatory drugs (NSAIDs) on disease activity in patients with stable ankylosing spondylitis (AS) receiving tumor necrosis factor inhibitor (TNFi). In this retrospective observational study, a total of 189 patients with stable AS receiving TNFi were included. Patients were classified into NSAID withdrawn group (n = 48) and NSAID continued group (n = 141), according to the use of NSAIDs. Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) were measured every 3 months, and Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) was measured every 6 months as parameters to evaluate disease activity. ESR, CRP, and BASDAI at each time point, and time-averaged values of each parameter during the observation period of 1 year were compared between the two groups. Repeated-measure ANOVA was performed to compare changes in disease activity parameters during the observation period between the two groups. The level of ESR, CRP, and BASDAI at baseline and during the observation period did not differ between the two groups. The time-averaged values of ESR (p = 0.096), CRP (p = 0.136), and BASDAI (p = 0.421), and changes of ESR (p = 0.101), CRP (p = 0.714), and BASDAI (p = 0.613) during the observation period were not significantly different between the two groups. The continued use of NSAIDs in patients with stable AS receiving TNFi had no additional benefit in controlling the disease activity, as compared to patients who withdrew NSAIDs. Considering the risk of toxicity of long-term NSAID use, withdrawal of NSAIDs in stable AS patients receiving TNFi may be preferable.