POS1474-HPR VALIDATION OF THE DANISH TRANSLATION OF THE ILLNESS INTRUSIVENESS RATING SCALE IN PATIENTS WITH RHEUMATIC DISEASE

Background: Rheumatic diseases [1, 2, 3], including rheumatoid arthritis, axial spondyloarthritis, psoriatic arthritis, fibromyalgia, and osteoarthritis, profoundly impact individuals' physical, psychological, and social well-being, making self-management a critical component of care. Self-management encompasses the individual's ability to manage symptoms, treatment, physical and psychosocial consequences, and lifestyle changes associated with chronic conditions [4]. However, validated instruments to measure self-management in diverse contexts remain limited. The Illness Intrusiveness Rating Scale (IIRS) was originally developed in English for chronic, disabling, or life-threatening diseases. It has since been employed across a range of conditions, demonstrating promise in evaluating self-management interventions for rheumatic diseases by assessing the severity and disruptiveness of illness [5]. The IIRS comprises 13 items scored on a seven-point rating scale, with total scores ranging from 13 to 91. To date, the IIRS has not been translated into Danish. Objectives: This study aimed to translate the IIRS into Danish and assess its psychometric properties in Danish patients with rheumatic diseases. Methods: Following COSMIN guidelines [6], the IIRS was translated and culturally adapted using a multi-step process that included forward and backward translations and cognitive interviews. Data for psychometric testing were collected from patients referred to the Danish Rheumatism Association's rehabilitation center, Sano. These patients were considered stable regarding disease activity. Participants provided demographic information, such as gender, age, and diagnosis, alongside their initial IIRS responses. To assess test-retest reliability, participants completed the questionnaire twice, approximately 14 days apart. Psychometric testing included evaluations of internal construct validity via Confirmatory Factor Analysis, internal consistency using Cronbach's α, test-retest reliability, standard error of measurement, and responsiveness through minimal detectable change. Results: The translation process yielded a consensus version of the IIRS that was well-understood by participants, with minor issues identified in specific items, such as the relevance of the "religious expression" item. A total of 192 participants completed the questionnaire over an 8-month period in 2023, with 99 participants completing the test-retest phase. The sample was 68% female, with a mean age of 62 years. The Danish IIRS demonstrated high internal consistency (Cronbach's α = 0.92). The correlation with total IIRS score ranged from 0.30-0.86 (Table 1). The inter-item correlations ranged between 0.15-0.87 (Table 1), with items 2 and 12 showing the lowest correlation and items 9, 10 and 13 the highest. Confirmatory Factor Analysis (Figure 1) confirmed the three-factor structure of the original scale, with acceptable model fit (comparative fit index=0.94, Root Mean Square Error of Approximation=0.10). Strong correlations were observed for items related to "Relationships and Personal Development" and "Instrumental" life domains, although the "Diet" item did not meet criteria for factor assignment. In the test-retest analysis we found that the minimal detectable change ranged 1.07-4.68. The coefficients of stability ranged from 0.63 to 0.82, with to items below 0.7. The Inter Class Correlation Coefficients (ICC) ranged from 0.40 to 0.99. In total 5 out of 13 items were at or above the 0.7 threshold for acceptable ICC. Domain scores for ICC ranged from 0.45-0.46, which indicate poor reliability. Cronbach's α between timepoint1 and timepoint2 ranged between 0.78 and 0.92, showing acceptable α scores. Conclusion: The Danish version of the IIRS demonstrated reliable and valid psychometric properties, making it a valuable tool for assessing the impact of rheumatic diseases and evaluating self-management interventions in Danish populations. Figure 1The confirmatory factor analysis REFERENCES: [1] J.S. Smolen, D. Aletaha, A. Barton, G.R. Burmester, P. Emery, G.S. Firestein, A. Kavanaugh, I.B. McInnes, D.H. Solomon, V. Strand, K. Yamamoto, Nat. Rev. Dis. Primer 4 (2018) 18001. [2] M.J. Cook, S.M.M. Verstappen, M. Lunt, T.W. O'Neill, Arthritis Care Res. 74 (2022) 1989–1996. [3] M. Glattacker, U. Opitz, W.H. Jäckel, Br. J. Health Psychol. 15 (2010) 367–387. [4] K.R. Lorig, H. Holman, Ann. Behav. Med. Publ. Soc. Behav. Med. 26 (2003) 1–7. [5] G.M. Devins, R. Dion, L.G. Pelletier, C.M. Shapiro, S. Abbey, L.R. Raiz, Y.M. Binik, P. McGowan, N.G. Kutner, H. Beanlands, S.M. Edworthy, Med. Care 39 (2001) 1097–1104. [6] L.B. Mokkink, C.A. Prinsen, D.L. Patrick, J. Alonso, L.M. Bouter, H.C. de Vet, C.B. Terwee, (n.d.) 32. Acknowledgements: We sincerely thank all the people with rheumatic disease who generously contributed to this study. Disclosure of Interests: None declared . © The Authors 2025. This abstract is an open access article published in Annals of Rheumatic Diseases under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Neither EULAR nor the publisher make any representation as to the accuracy of the content. The authors are solely responsible for the content in their abstract including accuracy of the facts, statements, results, conclusion, citing resources etc.

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