E038 A common measure of the impact of glucocorticoids in patients with inflammatory and autoimmune conditions - the Steroid PRO: A cross-cultural validation study with Rasch models
Authors: Bridgewater Susan , Ndosi Mwidimi , Dawson Jill , Richards Pamela , Silverthorne Christine , Dures Emma , Goodman Susan , Hill Catherine , Mackie Sarah L , Robson Joanna C 
Published: April 2023

Abstract

Background/Aims
Systemic glucocorticoids are key in the management of life- and organ-threatening rheumatic diseases, but have wide-ranging adverse effects of concern to patients and clinicians. We aimed to validate a Patient Reported Outcome (PRO) measure (the Steroid PRO) for assessing the impact of glucocorticoids on health-related quality of life (HRQoL) in patients receiving glucocorticoids for rheumatic disease.

Methods
This was a cross-sectional study of adults from the UK, USA, Australia and New Zealand, taking glucocorticoids for a rheumatic disease. An online survey was conducted at two time points: Time 1: (i) demographics - age, gender, country, ethnicity, educational level; (ii) clinical information - diagnosis, glucocorticoid dose; (iii) 40 candidate items for the Steroid-PRO, developed in a previous qualitative study; (iv) EQ5D-5L. Time 2 (optional, completed 3-5 days later): (i) the Steroid PRO candidate items; (ii) a condition change question. The survey was distributed via social media and patient organisations. After descriptive analysis, iterative testing with Rasch measurement model and exploratory factor analysis (EFA) informed item reduction and established structural validity, reliability and unidimensionality of the final Steroid-PRO. Item reduction was based on clinical importance, lack of fit to the Rasch model, and redundancy. Evidence of discriminative validity of the Steroid-PRO was established by comparing its scores for participants receiving lower dose glucocorticoid (up to 10 mg) versus higher dose (&gt;10 mg). Intraclass correlation (ICC) between Time 1 and Time 2 was calculated for patients who reported ‘no change’ compared with 3-5 days ago.

Results
A total of 946 patients returned complete responses at Time 1 (Time 2: 447 responses). They were from UK, n = 743 (78.5%); USA, n = 139 (14.7%); Australia, n = 59 (6.2%). Their mean age was 57.6 (SD = 13.6); 833 (88%) were women. They were treated for inflammatory arthritis (n = 194), connective tissue disease and/or vasculitis (n = 398), and giant cell arteritis and/or polymyalgia rheumatica (n = 341). A total of 25 items were removed due to floor effects and lack of fit to the Rasch model. The remaining 15 items showed a satisfactory fit to the model. EFA suggested a scale structure with four domains: Participation (4 items), Appearance (3 items), Psychological (5 items), and Treatment concerns (3 items). This 4-domain structure was supported by the Rasch model, confirming construct validity; χ2=47.82 (DF = 36), p = 0.899; and reliability (Person Separation Index, PSI=0.757). Patients on a lower glucocorticoid dose had lower Steroid-PRO domain scores than those receiving higher dose (discriminant validity). ICC between Time 1 and Time 2 ranged from 0.892 to 0.942 (95%CI 0.868 to 0.953) suggesting excellent (test-retest) reliability.

Conclusion
The final Steroid-PRO is a 15-item, valid and reliable 4-domain scale measuring the impact of glucocorticoid therapy on HRQoL of people with rheumatic diseases.
Disclosure
S. Bridgewater: Grants/research support; S.B. has received funding for research from Vifor Pharma. M. Ndosi: Grants/research support; M.N. has received funding for research from Vifor Pharma. J. Dawson: None. P. Richards: None. C. Silverthorne: None. E. Dures: Grants/research support; E.D. has received funding for research from Vifor Pharma. S. Goodman: Consultancies; S.G. reports consultancy for UCB. Grants/research support; S.G. has received research support from Novartis. Other; S.G. has given talks for NYU, Case Western, ACR Rheumatology Courses. C. Hill: None. S.L. Mackie: Consultancies; S.L.M. has provided consultancy on behalf of her institution for Roche/Chugai, Sanofi, AbbVie, AstraZeneca. Grants/research support; S.L.M. has been an investigator on clinical trials for Sanofi and GSK, as a research grant co-applicant, S.L.M. has received research funding (partial salary support) from Vifor, paid to her institution. Other; S.L.M. has given talks on behalf of her institution for Pfizer, Vifor and UCB. In all cases fees were paid to her institution and no personal fees were received, S.L.M. was supported by Roche to attend EULAR2019 and by Pfizer to attend ACR2021 virtually. J.C. Robson: Consultancies; J.C.R. reports: Consultancy for Vifor Pharma. Grants/research support; Funding for research from Vifor Pharma. Other; Speaking fees from Vifor Pharma.