Validity and utility of a single-item patient-reported measure of treatment-related bother in rheumatoid arthritis: A cross-sectional OMERACT study

OBJECTIVES: To assess the construct validity of a modified single-item measure of bother due to side effects (the GP5 item) from the Functional Assessment of Chronic Illness Therapy (FACIT) system by comparing it to current symptomatic side effects from the Patient-Reported Outcomes of the Common Terminology Criteria for Adverse Events (PROCTCAE) reported by patients with rheumatoid arthritis (RA). METHODS: Through a cross-sectional, web-based survey we collected information on the frequency of symptomatic side effects and bother from side effects related to RA medications. We applied multiple correspondence analysis (MCA) to reduce 80 symptomatic side effects into key dimensions (≥5% of the total variance each). We then examined associations among key dimensions, individual items, the sum of current side effects, and the single-item bother measure using Spearman rho. RESULTS: A total of 560 patients participated in the online survey. Our scree plot showed a clear elbow point after the first dimension, indicating that keeping just one dimension captured the most meaningful information. This overall side effect burden score appeared to reflect a broad concept influenced by a variety of symptomatic side effects, each having only a negligible to weak impact. CONCLUSIONS: Our results may indicate that individuals have diverse experiences of side effects, allowing the global index to capture these variations, even when they differ across patients. Thus, a single-item burden measure to side effects can potentially serve as a useful summary indicator, shedding light on the impact of symptomatic side effects experienced by RA patients.