POS0969 UNVEILING AXIAL INVOLVEMENT IN PSORIATIC ARTHRITIS: AN ANCILLARY ANALYSIS OF THE ASAS-perSpA STUDY
Authors: Benavent D. , Plasencia C. , Poddubnyy D. , Kishimoto M. , Proft F. , Sawada H. , López-Medina C. , Dougados M. , Navarro-Compán V. 
Published: May 2021

Background:Heterogeneity in psoriatic arthritis (PsA) is a current matter of discussion, especially concerning axial involvement.Objectives:To determine the profile of axial PsA (axPsA) in a worldwide setting. Secondly, to identify predictive factors associated with the development of axial involvement in patients with PsA.Methods:Data from 3684 patients with axial spondyloarthritis (axSpA) or PsA from the ASAS-PerSpA study were analysed. The ASAS-PerSpA is an observational, cross-sectional study that recruited consecutive patients with SpA from 68 centers worldwide. For this analysis, 367 PsA patients ever presenting axial involvement according to their rheumatologist were defined as axPsA and compared with 2651 axSpA patients, using logistic regression to later identify predictive factors for rheumatologist diagnosis of axPsA. In addition, the axPsA patients were also compared with 666 PsA patients without axial involvement (pPsA) and the characteristics associated with axial manifestations were determined by logistic regression analysis.Results:Among all patients, 2651 were identified as axSpA and 1033 patients as PsA. Among those with axial involvement, 2651 were identified as axSpA (100% of axSpA) and 367 as axPsA (35.5 % of PsA). In comparison with axSpA, axPsA patients were less frequently males, older, less frequently HLA-B27 positive and had a higher body mass index (Table 1). Additionally, while patients with axPsA had more peripheral manifestations and psoriasis, concomitant IBD and uveitis were higher in axSpA. In the multivariable analysis, older age at diagnosis (OR= 1.04), peripheral arthritis (OR= 7.32) and dactylitis (OR= 2.82) were significantly associated with a diagnosis of axPsA. However, uveitis (OR= 0.22), IBD (OR= 0.12) or HLA*B27 carriership (OR= 0.26) were inversely associated with axPsA diagnosis as compared to axSpA. Furthermore, axial involvement in patients with PsA was significantly associated with male gender (OR= 1.68), elevated CRP (OR= 2.87), and the absence of psoriasis (OR= 0.33).Conclusion:In this worldwide setting, axPsA was defined by rheumatologists as a unique phenotype, with disease features lying between axSpA and pure pPsA. Male gender, elevated CRP and the absence of psoriasis were associated with axial involvement in patients with PsA.Table 1.Demographic and disease characteristics of patients with axial involvement included in the ASAS PerSpA study. Results shown as absolute numbers (percentages) or as the mean ± standard deviationaxSpAn= 2651axPsAn= 367p-valueSex (male)1816 (68.5) 196 (53.4)<0.001Age at study visit42.1(13.0)50.0 (12.7)<0.001Body Mass Index25.9 (5.1)27.4 (5.7)<0.001Family history of SpA944 (35.6)135 (36.8)0.684Past history or current symptoms of back pain2625 (99.0)358 (97.5)0.04Inflammatory back pain (ASAS definition), n/N(%)2500/2632 (94.9)317/362 (87.6)<0.001Sacroiliitis on imaging, n/N (%) by: xRay mNY criteria1997/2586 (77.2)185/298 (62.1)<0.001 MRI-SIJ, ASAS definition1449/1757 (82.4)141/225 (62.6)<0.001 mNY criteria or ASAS definition2446/2634 (92.9)243/339 (71.7)<0.001HLA B27 positive1674 /2126 (78.7)54/182 (29.6)<0.001Elevated CRP (>5 mg/dL)1863/2569 (72.5)274/356 (76.9)0.2Classification criteria ASAS criteria2339 (88.2)185 (50.4)<0.001 CASPAR criteria123 (4.6)274 (74.4)<0.001Peripheral Arthritis946 (35.7)318 (86.6)<0.001Enthesitis1086 (41.0)198 (54.0)<0.001Dactylitis155 (5.8)125 (34.1)<0.001Psoriasis185 (7.0)324 (88.3)<0.001IBD129 (4.9)3 (0.8)<0.001Uveitis576(21.7)13 (3.5)<0.001csDMARD (ever)1359 (51.3)339 (92.4)<0.001bDMARD (ever)1585 (59.8)263 (71.7)<0.001Specific drug for axial involvementNSAIDs2465 (98.6)317 (96.1)0.002csDMARD828 (33.1)187 (56.7)<0.001bDMARD1288 (51.5)180 (54.4)0.32axSpA: axial spondyloarthritis; axPsA: axial psoriatic arthritis; IBD: Inflammatory Bowel Disease; CRP: C-Reactive Protein; mNY: modified New York; csDMARDs: conventional synthetic DMARDs; bDMARDs: biological DMARDs; NSAID: Non-steroidal anti-inflammatory drugsDisclosure of Interests:Diego Benavent: None declared, Chamaida Plasencia: None declared, Denis Poddubnyy: None declared, Mitsumasa Kishimoto Consultant of: AbbVie, Amgen-Astellas BioPharma, Asahi-Kasei Pharma, Astellas, Ayumi Pharma, BMS, Chugai, Daiichi-Sankyo, Eisai, Eli Lilly, Gilead, Janssen, Kyowa Kirin, Novartis, Ono Pharma, Pfizer, Tanabe-Mitsubishi, Teijin Pharma, and UCB Pharma., Fabian Proft Grant/research support from: AbbVie, AMGEN, BMS, Celgene, MSD, Novartis, Pfizer, Roche, UCB, Haruki Sawada: None declared, Clementina López-Medina: None declared, Maxime Dougados: None declared, Victoria Navarro-Compán: None declared.