Development and evaluation of RhizoQOL, a quality-of-life caregiver-reported survey for rhizomelic chondrodysplasia punctata, a rare peroxisomal disorder

Abstract

Background Rhizomelic chondrodysplasia punctata (RCDP) is a rare genetic disorder characterized by symptoms such as respiratory dysfunction, seizures, orthopedic issues, and neurodevelopmental delay. Potential therapeutics for RCDP warrant the development of clinical outcome assessments to assess the efficacy of treatment and the well-being of patients. Our study aimed to develop a valid quality-of-life (QOL) caregiver-reported survey instrument, RhizoQOL, to be used as an endpoint in RCDP clinical trials. Methods Development of the RhizoQOL survey tool included three RCDP caregiver focus groups to elicit concepts to serve as potential domains in a QOL survey instrument for RCDP, pilot survey development and initial testing, cognitive interviewing of revised survey drafts to determine content validity, as well as a three-month longitudinal study for reliability and internal consistency of the survey instrument. Results Twenty-eight caregivers participated in the focus groups, reporting that concepts that could be appropriate domains of QOL in RCDP include psychosocial behavior, feeding symptoms, mobility symptoms, respiratory symptoms, seizures and related activity, and impact of treatment. Following pilot survey testing (n = 22) and stakeholder feedback, a revised pilot survey instrument was administered to five caregivers for cognitive interviewing. This resulted in a revised survey instrument with 31 question items, six domains, and a 1–5 Likert scale item response assessing frequency or severity of event in the question item. Longitudinal testing (n = 18) of the revised survey instrument found the average response score was 1.98 ± 0.97 for all question items, and a Cronbach’s alpha value of 0.856, suggesting strong intra-survey question reliability. Using individual question item results from reliability testing, linear regression modeling, and testing for required magnitude of significant treatment effects, eight question items were removed from the survey instrument, resulting in a total of 23 question items within 6 discrete domains. Conclusions The final RhizoQOL survey instrument, consisting of 23 questions, assesses the symptoms and experiences of RCDP patients as observed by caregivers and serves as a novel clinical outcome assessment for RCDP therapeutic clinical trials to assess the impacts of RCDP and the effectiveness of treatments.