Supplementary Material for: Preparation and Rationale for a Patient-Reported Clinical Outcome Assessment Set of Fluid Overload for Drug Development in Nephrotic Syndrome

Introduction: Fluid overload is a source of substantial morbidity for adults and children with nephrotic syndrome (NS). Preparation and Rationale for a Fluid Overload in Nephrotic Syndrome Clinical Outcomes Assessment Set for Drug Development (Prepare-NS, 5UG3FD007308) was funded by the U.S. Food and Drug Administration to develop a core set of patient-reported and observer-reported (for young children) outcome measures of fluid overload for use in pharmaceutical trials across the lifespan. Methods: The Prepare-NS study team developed the proposed context of use with input from stakeholders. We conducted a scoping review to assess the available literature on relevant patient- and observer-reported measures and performed secondary analyses of existing qualitative and quantitative data. Results: The outcome set will aim to serve individuals two years of age and older with primary nephrotic syndrome conditions (specifically focal segmental glomerulosclerosis, minimal change disease, IgM nephropathy, membranous nephropathy, and childhood–onset nephrotic syndrome not biopsied). The existing literature describing patient reported outcomes in nephrotic syndrome largely relies on non-specific measures of health-related quality of life; fluid overload has been associated with lower scores on these measures. Conclusion: To address the gap in measure availability and fluid overload content, the Prepare-NS team has launched a set of qualitative studies for concept elicitation from the population of interest to inform development of new measures. The resulting measures subsequently will undergo psychometric evaluation and validation in a survey study.