Development of a conceptual model for fluid overload in children with nephrotic syndrome: a qualitative study of parent-reported observable experiences

Background Nephrotic syndrome (NS) is characterized by persistent or relapsing and remitting fluid overload. To identify the effectiveness of clinical treatments that target fluid overload among young children with NS, researchers seek to better understand the observable signs, events, or behaviors related to fluid overload among children too young to reliably self-report. This manuscript describes a conceptual model developed to inform an observer-reported outcome (ObsRO) appropriate for evaluating fluid overload in young children with NS. Methods Semistructured interviews were conducted with caregivers of children aged 2–11 with NS via Zoom videoconferencing, telephone, or in-person. Eligible NS diagnoses were focal segmental glomerular sclerosis, minimal change disease, IgM nephropathy, membranous nephropathy, or childhood-onset NS not biopsied. Thematic content analysis was used to identify major themes in parent characterizations of their children’s experience with fluid overload. Results Twenty-six caregivers of children with NS completed interviews. Interview content demonstrated that swelling had an impact on physical functioning (upper extremity function, activities of daily living, and mobility/walking), physical symptoms (appetite, fatigue, gastrointestinal distress, pain, and sleep), essential function (breathing, urination, and vision), behavior (crying and irritability), and social functioning (included daycare/school, family/friend relationships, and recreational activities). Conclusions Domains will inform development of a clinical outcome assessment set for a validation study.