POS0995 EFFECT OF SEX IN CO-EXISTENT FIBROMYALGIA AND ENTHESITIS IN SPONDYLOARTHRITIS: ANCILLARY ANALYSIS OF THE ASAS-PerSpA STUDY
Authors: G. Fitzgerald, S. Maguire, F. B. O’shea, C. López-Medina, M. Dougados, N. Haroon
Journal: Annals of the Rheumatic Diseases (2021)

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 &amp; 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&lt;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&lt;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&lt;0.01). Table 1. Participant characteristics, stratified by sex. Values are mean (SD), median (25 th , 75 th ) or n (%). P-values are independent T-tests or Mann-Whitney as appropriate. Variable Total Male Female P value N 4465 2724 1741 Age, years 45 (14) 43 (14) 46 (13) &lt;0.01 Disease duration, years 11 (6, 20) 12 (6, 21) 11 (5, 19) 0.01 Delay to diagnosis, years 3 (1, 9) 3 (1, 9) 3 (1, 10) 0.11 HLA-B27 positive 2066 (66) 1457 (73) 609 (54) &lt;0.01 Radiographic sacroiliitis 2517 (61) 1788 (70) 729 (46) &lt;0.01 Sacroiliitis on MRI 1817 (65) 1128 (68) 689 (60) &lt;0.01 axSpA ASAS criteria 2910 (65) 1953 (72) 957 (55) &lt;0.01 pSpA ASAS criteria 555 (12) 250 (9) 305 (18) &lt;0.01 CASPAR criteria 1043 (23) 508 (19) 535 (31) &lt;0.01 BMI, kg/m 2 26 (23, 29) 26 (23, 29) 26 (23, 30) 0.24 Axial involvement 3428 (76.8) 2243 (82.3) 1185 (68.1) &lt;0.01 Peripheral involvement 2541 (56.9) 1404 (51.5) 1137 (65.3) &lt;0.01 Enthesitis 1984 (44.4) 1149 (42.2) 835 (48.0) &lt;0.01 Uveitis 738 (17) 482 (18) 256 (15) 0.01 Psoriasis 1212 (27) 615 (23) 597 (34) &lt;0.01 Inflammatory bowel disease 275 (6) 150 (6) 125 (7) 0.02 Enthesitis 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&lt;0.01) longer delay to diagnosis of 1.8 years and a higher BMI of 2.1 kg/m 2 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&lt;0.01) and ASDAS-CRP (3.5 vs 2.5, p&lt;0.01), with no difference between sexes (p&gt;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.