A non-interventional observational study to identify and validate clinical outcome assessments for adults with phenylketonuria for use in clinical trials

• Published in: Molecular genetics and metabolism reports 2021-12, Vol.29, p.100810-100810, Article 100810
• Main Authors: Burton, Barbara K., Skalicky, Anne, Baerwald, Christoph, Bilder, Deborah A., Harding, Cary O., Ilan, Aaron B., Jurecki, Elaina, Longo, Nicola, Madden, David T., Sivri, H. Serap, Wilcox, Gisela, Thomas, Janet, Delaney, Kathleen
• Format: Article
• Language: English
• Subjects: Adults; Clinical outcome assessments; Clinician-reported outcomes; Observer-reported outcomes; Patient-reported outcomes; Phenylketonuria; PKU; Research Paper
• ISSN: 2214-4269; 2214-4269
• DOI: 10.1016/j.ymgmr.2021.100810

Current clinical outcome assessments (COAs) are not effectively capturing the complex array of symptoms of adults with phenylketonuria (PKU). This study aimed to identify concepts of interest relevant to adults with PKU. Based on these concepts, COAs for patient-reported outcomes (PROs), observer-reported outcomes (ObsROs), and clinician-reported outcomes (ClinROs) were selected or developed and content validity was assessed. Concept-elicitation interviews were conducted with an international cohort of adults with PKU (n = 30), family member observers (n = 14), and clinical experts (n = 8). Observers and clinical experts were included to overcome the risk of lack of self-awareness among adults with PKU. The concepts of interests endorsed by ≥30% of patients, observers, and/or clinical experts were selected, mapped to items in existing COAs, and used to develop global impression items for patients, observers, and clinicians. Next, the content validity of the COAs and global impression items was evaluated by cognitive interviews with patients (n = 22), observers (n = 11), and clinical experts (n = 8). All patients were categorized according to blood phenylalanine (Phe) levels (i.e., 1200 μmol/L). Concepts of interests were identified across four domains: emotional, cognitive, physical, and behavioral. After mapping, eight existing COAs were selected based on the concept coverage (six PROs, one ObsRO, and one ClinRO). The six PRO measures were considered as potentially fit-for-purpose. The ObsRO measure was not deemed relevant for use in observers of adults with PKU and only a subscale of the ClinRO measure was considered valid for assessing adults with PKU by clinicians. Due to the lack of existing COAs covering all concepts of interests, global impression items for symptom severity and change in symptoms were developed, which were limited to one question covering in total 14 concepts. Upon validation, some of the patient and observer global impression items were excluded as they were subject to lack of insight or could not be reported by observers. Due to the limited interaction time between clinician and patient, use of the clinician global impression items was not supported. Existing COAs relevant to adults with PKU were selected and PKU-specific global impression items were developed by mapping the most frequently identified concepts of interests from internationally-conducted in-depth interviews. Future studies should