Effect Of Sex In Co-Existent Fibromyalgia And Enthesitis In Spondyloarthritis: Ancillary Analysis Of The Asas-Perspa Study

Background:Enthesitis is a common feature of axial spondyloarthropathy (axSpA) and psoriatic arthritis (PsA). Up to 25% of individuals with axSpA and PsA have a co-existing diagnosis of fibromyalgia syndrome (FMS). The anatomic overlap between tender points in FMS and sites of entheses is a challenge when differentiating between active SpA and FMS. Literature investigating the co-existence of enthesitis and FMS in individuals with SpA is sparse, in particular the effect of sex. The ASAS Peripheral involvement in Spondyloarthritis (PerSpA) study aims to characterize peripheral musculoskeletal in individuals with SpA across the world.Objectives:(1)To characterise the co-existence of enthesitis and FMS in individuals with SpA.(2)To explore the effect of sex on the presence of FMS and enthesitis.Methods:All individuals from the cross-sectional multinational ASAS-PerSpA study with a diagnosis of axSpA, peripheral SpA (pSpA) or PsA according to their rheumatologist were included. The Fibromyalgia Rapid Screening Tool (FiRST) was used to make the diagnosis of FMS. The baseline descriptive and clinical differences between sexes were performed using T-tests and crosstabs. Sex-stratified comparisons within the following categories were conducted using chi-square analysis and ANOVA as appropriate: (1) enthesitis & fibromyalgia; (2) enthesitis only; (3) fibromyalgia only; (4) neither.Results:Baseline characteristics of the 4465 included patients are outlined in Table 1, stratified by sex. Enthesitis occurred in 44% (n=1984) of the population and was more common in females than males (48% vs 42%, p<0.01). The majority affected had intermittent episodes of enthesitis (55%, n=1088), with the Achilles tendon and plantar fascia the two most common sites in both sexes. Enthesitis was more often confirmed on imaging in females than males (44% v 35%, p<0.01). The most common treatment for enthesitis was non-steroidal anti-inflammatories (97%, n=1318), with no difference when stratified by sex. FMS occurred in 19% (n=775) of patients and was more common in females than males (28% vs 13%, p<0.01).Table 1.Participant characteristics, stratified by sex. Values are mean (SD), median (25th, 75th) or n (%). P-values are independent T-tests or Mann-Whitney as appropriate.VariableTotalMaleFemaleP valueN446527241741Age, years45 (14)43 (14)46 (13)<0.01Disease duration, years11 (6, 20)12 (6, 21)11 (5, 19)0.01Delay to diagnosis, years3 (1, 9)3 (1, 9)3 (1, 10)0.11HLA-B27 positive2066 (66)1457 (73)609 (54)<0.01Radiographic sacroiliitis2517 (61)1788 (70)729 (46)<0.01Sacroiliitis on MRI1817 (65)1128 (68)689 (60)<0.01axSpA ASAS criteria2910 (65)1953 (72)957 (55)<0.01pSpA ASAS criteria555 (12)250 (9)305 (18)<0.01CASPAR criteria1043 (23)508 (19)535 (31)<0.01BMI, kg/m226 (23, 29)26 (23, 29)26 (23, 30)0.24Axial involvement3428 (76.8)2243 (82.3)1185 (68.1)<0.01Peripheral involvement2541 (56.9)1404 (51.5)1137 (65.3)<0.01Enthesitis1984 (44.4)1149 (42.2)835 (48.0)<0.01Uveitis738 (17)482 (18)256 (15)0.01Psoriasis1212 (27)615 (23)597 (34)<0.01Inflammatory bowel disease275 (6)150 (6)125 (7)0.02Enthesitis and FMS occurred together in 10% of the cohort, was more common in women than men (see Figure 1) and was associated with a significantly (p<0.01) longer delay to diagnosis of 1.8 years and a higher BMI of 2.1 kg/m2 than people with enthesitis only. Objective confirmation of enthesitis was similar in those with and without FMS (38% vs 38%, p=0.92).The presence of FMS added to the burden of disease in those with enthesitis as assessed by BASDAI (6.4 vs 3.6, p<0.01) and ASDAS-CRP (3.5 vs 2.5, p<0.01), with no difference between sexes (p>0.05).Conclusion:In this large cross-sectional multinational analysis, FMS affected 19% of individuals with SpA. The co-existence of enthesitis and FMS occurred in 16% of females compared to 6% of males. The presence of FMS increased the burden of disease in those with enthesitis, as assessed by BASDAI and ASDAS-CRP, with no difference between men and women.Disclosure of Interests:Gillian Fitzgerald: None declared, Sinead Maguire Grant/research support from: Recipient of Gilead Inflammation Fellowship, Finbar Barry O’Shea: None declared, Clementina López-Medina: None declared, Maxime Dougados: None declared, Nigil Haroon Speakers bureau: Received honorarium from AbbVie, Eli Lilly, Jannsen, Novartis, UCB, Consultant of: AbbVie, Eli Lilly, Jannsen, Novartis, UCB, Grant/research support from: AbbVie, Eli Lilly, Jannsen, Novartis, UCB.