Development of a new patient-reported outcome measure to assess activities and participation in people with systemic sclerosis: the Cochin 17-item Scleroderma Functional scale

Abstract

Background: Patient-reported outcome measures (PROMs) aimed at assessing people with systemic sclerosis (SSc) have rarely involved the target population in the item- and domain-generation stage of the instrument construction.

Objectives: To develop a new PROM assessing activities and participation in people with SSc.

Methods: A provisional International Classification of Functioning, Disability and Health (ICF)-based 65-item questionnaire previously developed from interviews of people with SSc was sent by email to all patients followed in the internal medicine department of Cochin hospital (n = 184) and enrolled in the Scleroderma Patient-centered Intervention Network Cohort. Items were reduced according to their metric properties. Dimensional structure of the questionnaire was assessed by principal component analysis, convergent and divergent validities by Spearman's rank correlation coefficient, internal consistency by Cronbach's α, and reliability by a test-retest method using the intraclass correlation coefficient (ICC) and Bland-Altman analysis.

Results: Overall, 113 of 184 patients (61·4%) completed the provisional questionnaire. The item-reduction process resulted in a 17-item questionnaire, the Cochin 17-item Scleroderma Functional scale (CSF-17). Principal component analysis extracted two dimensions: 10 items related to mobility (CSF-17 section A) and seven items related to general tasks (CSF-17 section B). We observed convergent validity of the CSF-17 total score with global activity limitation, pain, depression and aesthetic burden, and divergent validity with anxiety. Cronbach's α was 0·94 for section A and 0·95 for section B. ICC (n = 25 patients) was 0·92 for the CSF-17 total score. Bland-Altman analysis did not reveal a systematic trend for the test-retest.

Conclusions: The CSF-17 is a new PROM assessing activities and participation specifically in people with SSc. Its content and construct validities are very high. What is already known about this topic? In the earliest stages of construction patient-reported outcomes (PROMs) for people with systemic sclerosis (SSc) rarely involve the target population. Instruments able to capture the specific needs of people with SSc in terms of activities and participation are lacking. What does this study add? The Cochin 17-item Scleroderma Functional Scale (CSF-17) is a new PROM assessing global activities and participation specifically in people with SSc. Patients' perspectives were prioritized at all stages of construction. What are the clinical implications of this work? The CSF-17 could be used in clinical practice and research to assess the efficacy of complex multidisciplinary interventions targeting activity limitations and participation restriction in people with SSc. Linked Comment: Clark and Denton. Br J Dermatol 2020; 183:610.