The presence of fibromyalgia in patients who are undergoing treatment of spondyloarthritis (SpA) is associated with higher measures of disease activity and shorter duration of first-time treatment with tumor necrosis factor inhibitors, according to results of a study measuring the impact and prevalence of fibromyalgia coexisting with SpA.
The results confirm “that the existence of concomitant FM [fibromyalgia] in SpA might complicate the evaluation of treatment response and [suggest] that coexistence of FM should be carefully screened when initiating a TNFi [tumor necrosis factor inhibitor] and/or evaluating its treatment effect, especially in the presence of peripheral and/or enthesitic symptoms and in the presence of very severe disease activity and patient-reported scores,” wrote Dr. Natalia Bello and her colleagues at Cochin Hospital, Paris (Arthritis Res Ther. 2016 Feb 9;18:42. doi: 10.1186/s13075-016-0943-z).
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They recruited patients from Cochin Hospital, a tertiary care facility, and its rheumatology department’s outpatient clinic. Rather than use the 1990 American College of Rheumatology (ACR) classification criteria of FM or the 2010 ACR or modified 2010 ACR diagnostic criteria, which were developed for research and classification purposes, the investigators diagnosed FM based on a score of 5 or 6 on the six-question, self-reported Fibromyalgia Rapid Screening Tool (FiRST), which has 90.5% sensitivity and 85.7% specificity for FM. Patients’ SpA diagnoses were made by their rheumatologists. Overall, 30% of the cohort was female and had a mean age of 43 years.
The overall FM prevalence in the cohort was 21.4% (42 of 196 patients) and did not differ significantly according to whether the patients met either the clinical or imaging ASAS (Assessment of Spondyloarthritis International Society) criteria (21.3% vs. 18.8%, respectively) or whether they did or did not fulfill the ASAS criteria (21.1% vs. 30.0%, respectively).
Previous studies have shown the prevalence of FM at 12.6%-15.0% in SpA patients. Classifying axial SpA based on the clinical arm criteria alone has been controversial, the investigators said, mainly because it does not require an objective sign of inflammation (abnormal C-reactive protein or presence of inflammatory lesions seen on MRI of the sacroiliac joint) or structural damage in the sacroiliac joint seen on pelvic radiographs. But at least in this study there was no difference in FM prevalence in regard to whether patients met either the imaging and clinical arms of the ASAS classification criteria for axial SpA or both.
The study, according to the best knowledge of the investigators, is the first “to evaluate the prevalence of FM in a population of patients with SpA with regard to the fulfillment of the ASAS classification criteria.”
FM patients had as expected a significantly higher rate of either history of depression, or use of psychotropic drugs or strong opioids, compared with patients without FM (67% vs. 35%; P less than .01). Rates of exposure to treatment with different drug types (nonsteroidal anti-inflammatory drugs or conventional antirheumatic disease-modifying drugs) did not differ between those with and without FM, but FM patients switched significantly more often from their first TNFi (15.2% vs. 4.0%) and used it for a significantly shorter mean duration (1.7 vs. 3.5 years). The percentage of patients still taking their first TNFi after 2 years also was significantly lower among FM patients (28.1% vs. 41.7%).
Within the entire cohort, FM patients more often had enthesitis (59.5% vs. 39.0%, P = .01), a higher total Bath Ankylosing Spondylitis Disease Activity Index (4.7 vs. 2.6; P less than .01), higher global visual analog scale (5.9 vs. 3.0; P less than .01), and higher Bath Ankylosing Spondylitis Functional Index (4.8 vs. 2.0; P less than .01).
The authors suggested that FM patients’ higher rates of peripheral symptoms and enthesitis may warrant the use of the FiRST questionnaire in clinical practice before starting a TNFi in SpA patients to detect potentially coexisting FM.
The authors had no conflicts of interest to declare.