Fibromyalgia coexists in patients with axial spondyloarthritis (axSpA) and has a negative effect on tumor necrosis factor blocker (TNFb) therapy response, according to the results of a prospective, observational, longitudinal study (ClinicalTrials.gov identifier: NCT03039088) published in the Annals of the Rheumatic Diseases.
Fibromyalgia was defined by the Fibromyalgia Rapid Screening Tool (FiRST) at baseline, a sustained FiRST at the follow-up effectiveness visit, and the fulfillment of American College of Rheumatology 1990 criteria for fibromyalgia. The primary endpoint was the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI 50), adjusted on the basis of factors known to have an effect on TNFb response.
A total of 508 patients were included in the analysis, of whom 37.8% had fibromyalgia at baseline. After 12 weeks of TNFb therapy, fewer participants in the fibromyalgia group achieved the effectiveness endpoints, including BASDAI 50 (45.3% among patients with fibromyalgia vs 54.1% in the group without fibromyalgia, according to FiRST), but the difference was not statistically significant.
Changes in X-ray sacroiliitis (adjusted odds ratio [aOR], 1.7; 95% CI, 1.2-2.6) and abnormal C-reactive protein (CRP; aOR, 1.7; 95% CI, 1.2-2.5) were factors that were independently associated with a BASDAI 50 response. Almost all the other effectiveness endpoints were significantly less common among patients with fibromyalgia, except for the CRP change endpoints, in which there were no differences reported between the groups.
The investigators concluded that although the results demonstrate that the presence of comorbid fibromyalgia and axSpA has a negative effect on response to TNFb therapy, this effect appears to be related to the instruments used in its evaluation, rather than a treatment effect of the molecule in this subgroup of patients. Additional studies are warranted to confirm the results of this study and to assess the relevance of implementing the FiRST questionnaire in daily clinical practice.
Moltó A, Etcheto A, Gossec L, et al. Evaluation of the impact of concomitant fibromyalgia on TNF alpha blockers’ effectiveness in axial spondyloarthritis: results of a prospective, multicentre study. Ann Rheum Dis. 2018;77(4):533-540.