In patients with axial spondyloarthritis (axSpA), fulfilling the criteria for fibromyalgia had a modest effect on axSpA disease activity measures and quality of life (QoL), with no significant effect on the response to treatment with tumor necrosis factor (TNF) inhibitors, according to the results from a prospective UK national register published in Rheumatology.
The investigators sought to explore the extent to which comorbid fibromyalgia is associated with higher disease activity, worse QoL, and poorer response to TNF inhibitors in patients with axSpA. Participants from the British Society for Rheumatology Biologics Register of Axial Spondyloarthritis (BSRBR-AS) were recruited across 83 centers in the United Kingdom. A total of 1757 patients were eligible for the analyses, with 22.1% meeting the criteria for fibromyalgia.
Overall, patients with axSpA and comorbid fibromyalgia exhibited higher disease activity (Bath Ankylosing Spondylitis Disease Activity Index [BASDAI] average difference, 1.04; 95% CI, 0.75-1.33), and worse QoL (Ankylosing Spondylitis Quality of Life score difference, 1.42; 95% CI, 0.88-1.96), after adjustment for demographic, lifestyle, and clinical factors.
In 291 patients who initiated biologic therapy with TNF inhibitors, BASDAI scores in patients with comorbid fibromyalgia were 2.0 higher at baseline but decreased to 1.1 higher after 12 months of treatment. No significant difference was observed with respect to the likelihood of fulfilling Assessment of Spondyloarthritis International Society 20 criteria at 12 months. Lower rates of improvement in disease activity and QoL after 3 months of treatment with a TNF inhibitor were most strongly associated with high scores on the fibromyalgia Symptom Severity Scale (SSS) component.
The investigators concluded that in patients with axSpA and comorbid fibromyalgia, patients with a high SSS component on fibromyalgia assessment might benefit from additional management of their fibromyalgia. In these individuals, additional non-pharmacologic therapies aimed at targeting their symptoms and improving their outcomes should be considered by rheumatologists.