Validation of a patient-reported outcome measure for giant cell arteritis

Ndosi, Mwidimi; Almeida, Celia; Dawson, Jill; Dures, Emma; Greenwood, Rosemary; Bromhead, Alison; Guly, Catherine; Stern, Steve; Hill, Catherine; MacKie, Sarah; Robson, Joanna C

Abstract

OBJECTIVES: GCA is systemic vasculitis manifesting as cranial, ocular or large vessel vasculitis. A prior qualitative study developed 40 candidate items to assess the impact of GCA on health-related quality of life (HRQoL). This study aimed to determine final scale structure and measurement properties of the GCA patient reported outcome (GCA-PRO) measure. METHODS: Cross-sectional study included UK patients with clinician-confirmed GCA. They completed 40 candidate items for the GCA-PRO at times 1 and 2 (3 days apart), EQ-5D-5L, ICECAP-A, CAT-PROM5 and self-report of disease activity. Rasch and exploratory factor analyses informed item reduction and established structural validity, reliability and unidimensionality of the final GCA-PRO. Evidence of validity was also established with hypothesis testing (GCA-PRO vs other PRO scores, and between participants with 'active disease' vs those 'in remission') and test-retest reliability. RESULTS: The study population consisted of 428 patients: mean (s.d.) age 74.2 (7.2), 285 (67%) female; 327 (76%) cranial GCA, 114 (26.6%) large vessel vasculitis and 142 (33.2%) ocular involvement. Rasch analysis eliminated 10 candidate GCA items and informed restructuring of response categories into four-point Likert scales. Factor analysis confirmed four domains: acute symptoms (eight items), activities of daily living (seven items), psychological (seven items) and participation (eight items). The overall scale had adequate Rasch model fit (χ2 = 25.219, degrees of freedom = 24, P = 0.394). Convergent validity with EQ5D-5L, ICECAP-A and Cat-PROM5 was confirmed through hypothesis testing. Internal consistency and test-retest reliability were excellent. CONCLUSION: The final GCA-PRO is a 30-item, four-domain scale with robust evidence of validity and reliability in measuring HRQoL in people with GCA.

• Journal Article Type: Article
• Acceptance Date: Apr 4, 2023
• Online Publication Date: May 5, 2023
• Publication Date: Jan 31, 2024
• Deposit Date: Apr 4, 2023
• Publicly Available Date: May 6, 2024
• Journal: Rheumatology (Oxford, England)
• Print ISSN: 1462-0324
• Electronic ISSN: 1462-0332
• Publisher: Oxford University Press (OUP)
• Peer Reviewed: Peer Reviewed
• Volume: 63
• Issue: 1
• Pages: 181-189
• DOI: https://doi.org/10.1093/rheumatology/kead201
• Keywords: Giant cell arteritis, temporal arteritis, quality of life, Patient reported outcome measures, large vessel vasculitis, ocular GCA, Rasch analysis
• Public URL: https://uwe-repository.worktribe.com/output/10608980
• Publisher URL: https://academic.oup.com/rheumatology/advance-article/doi/10.1093/rheumatology/kead201/7152987