Psychometric evaluation of the Rheumatoid Arthritis Symptom Questionnaire (RASQ) in an observational study

Abstract

Objective: To describe the psychometric performance of the scores produced by the Rheumatoid Arthritis Symptom Questionnaire (RASQ), a new patient-reported outcome (PRO) questionnaire developed to assess the signs and symptoms of rheumatoid arthritis (RA).

Methods: Adult subjects with clinically confirmed RA completed a set of questionnaires (including the RASQ) at an initial study visit (Day 1), and then completed the RASQ and the Patient Global Impression of Change (PGI-C) on their own on Day 8. Demographic and health data were summarized using descriptive statistics, and psychometric analyses were conducted, including: acceptability, item and scale distribution, reliability (internal consistency and test–re-test reliability), and construct-related validity (convergent validity and known-groups methods).

Results: In total, 200 subjects (females = 61.5%; white = 72.0%; and age [mean] = 60.7 years) with RA were recruited across the US and included in the analysis. There were no missing data recorded for the RASQ, and scores were well distributed for both timepoints. The RASQ Total Symptom Score surpassed the threshold (α ≥ 0.70) for internal consistency at Day 1 (α = 0.967) and test–re-test score reliability (intra-class correlation coefficient [ICC] > 0.70) (ICC = 0.960). Convergent validity analyses demonstrated that the RASQ items and Total Symptom Score had high correlations (convergent validity) with other PRO questionnaires. Known-groups methods demonstrated that the RASQ (Total Symptom Score and all single items) can differentiate between clinically distinct groups.

Conclusions: The RASQ is capable of producing psychometrically sound scores when administered to adults with RA.

Keywords:

• Patient-reported outcome
• instrument development
• rheumatoid arthritis
• RA
• psychometric analysis

Transparency

Declaration of funding

Design, study conduct, and financial support for the study were provided by AbbVie Inc.

Declaration of financial/other relationships

MS and AG are employed by AbbVie and hold AbbVie stocks. BB, JS, CF, and AS are employed by Adelphi Values and were contracted by AbbVie to conduct the research activities reported in this manuscript. BB, JS, CF, and AS have also worked with other pharmaceutical companies on PRO instrument development projects. CMRO peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

Acknowledgments

The authors would like to acknowledge Megan Daggett of Adelphi Values for providing scientific writing assistance. AbbVie provided funding for this work.