POS0524 EXPLORING THE INTERRELATIONSHIPS OF DISEASE ACTIVITY, ILLNESS PERCEPTIONS, COPING STRATEGIES, PSYCHOLOGICAL WELLBEING, CENTRAL SENSITIZATION AND LIFESTYLE FACTORS IN AXIAL SPONDYLOARTHRITIS USING STRUCTURAL EQUATION MODELING
Authors: S. Kieskamp, Y. M. Van der Kraan, S. Arends, F. Wink, R. Stewart, D. Paap, J. P. L. Spoorenberg
Journal: Annals of the Rheumatic Diseases (2024)

<h3>Background:</h3> In a substantial part of patients with axial spondyloarthritis (axSpA), biological treatment is successful in reducing inflammation. However, disease activity scores may remain high (potentially due to factors beyond active inflammation. Pain mechanisms apart from nociception, such as central sensitization (CS), may contribute to this, underscoring the complexity of chronic pain in axSpA. Furthermore, biopsychosocial factors, including illness perception, coping strategies, psychological wellbeing and lifestyle factors, may also contribute to this complexity. The interplay of these factors and effect on disease activity assessments remains unclear. <h3>Objectives:</h3> Our study aim was to cross-sectionally explore the direct and indirect interrelationships between disease activity, CS, illness perceptions, coping strategies, psychological wellbeing, and lifestyle in axSpA, using Structural Equation Modeling (SEM). <h3>Methods:</h3> Data collected from consecutive outpatients from the Groningen Leeuwarden axSpA (GLAS) cohort, clinically diagnosed and fulfilling the ASAS classification criteria, were used in this study. Standardized assessments included Ankylosing Spondylitis Disease Activity Score (ASDAS), educational level, and body mass index (BMI). Additionally, participants completed questionnaires on central sensitization (CSI), illness perception (IPQ-R), pain catastrophizing (PCS), coping (CORS), anxiety and depression (HADS) and physical activity (mSQUASH). SEM is a multivariate analysis testing interrelationships between measured and latent variables in a structural model, and interpretation of results is comparable to a combination of factor analysis and multivariable regression. Variables analysed were: ASDAS total score, CSI score, highest attained education, BMI; and the latent variables perception (composed of PCS and IPQ-R subscale scores), active coping (composed of scores for behavioural coping styles: 'Decreasing Activity' and 'Pacing'), and psychological distress (composed of subscores of HADS). We hypothesized that these variables would have either a direct or indirect association with ASDAS. Incremental adjustments were made to enhance model fit, as determined by Akaike Information Criterion (lower equals better) and Bayesian Information Criterion (lower equals better) values. Only complete cases were incorporated into the final analysis. <h3>Results:</h3> Data from 301 axSpA outpatients were included in the final analysis. 61% were male, median time since diagnosis 22 [12-33] years and median ASDAS 2.2 [1.5-2.8]. After multiple iterations, we finalized the model (Figure 1.). The Root Mean Square Error of Approximation was 0.082 (95% CI 0.072-0.092), Comparative Fit Index was 0.840, and the χ<sup>2</sup>/df ratio 2.97, indicating acceptable model fit. Illness perception, CS, physical activity and BMI had a direct, independent association with ASDAS. The association of coping style with ASDAS was mediated by physical activity, while the association of illness perception with ASDAS was partly mediated by CORS and CSI. Psychological wellbeing (depression/anxiety) and educational level were indirectly associated with ASDAS through illness perception. <h3>Conclusion:</h3> This SEM conducted in our axSpA standard-of-care cohort showed that ASDAS represents disease activity multidimensionally. In daily clinical practice, it is important to recognize that factors besides inflammation may also have an effect on disease activity scores, of which central sensitization and illness perception seem to contribute most. <h3>REFERENCES:</h3> <b>NIL.</b> <h3>Acknowledgements:</h3> The authors would like to thank the ASAS for awarding the ASAS research grant to support this study. <h3>Disclosure of Interests:</h3> Stan Kieskamp: None declared, Yvonne M. van der Kraan: None declared, Suzanne Arends Argenx, Novartis, BMS, Galapagos, Freke Wink Novartis, Abbvie, Roy Stewart: None declared, Davy Paap: None declared, J.P.L Spoorenberg Novartis, Abbvie, Pfizer, UCB, Galapagos, Novartis