Objective: To perform qualitative research to develop and establish content validity of a new clinical outcome assessment (COA) instrument for paroxysmal movement disorders in Glut1 DS and their impact on physical functioning.

Background: Glut1 DS is a rare, genetic disorder characterized by impaired glucose transport to the brain, causing cerebral energy deficiencies. Glut1 DS symptoms can include seizures, cognitive impairments and/or paroxysmal movement disorders. The functional impact of the paroxysmal movement disorders is difficult to assess in-clinic due to their unpredictable onset. There are no COA instruments specific to Glut1 DS movement disorders. To address this gap the Paroxysmal Movement Disorder Diary was developed as a primary outcome measure for a phase 3 clinical trial in Glut1 DS.

Methods: The qualitative research included a literature review and concept elicitation (CE) interviews with clinicians (n=3), Glut1 DS patients (n=1) and caregivers (n=9). The CE interviews involved open-ended questions about the experience and observation of Glut1 DS movement disorders and associated impacts. Six of the caregivers submitted videos of their child experiencing movement disorders for qualitative analysis, review and commentary by expert clinicians. Verbatim transcripts were analyzed using Atlas ti software and thematic analysis methods. To provide insights regarding the relevance, understanding and usability of the diary, pilot testing and cognitive interviews of the diary are ongoing.

Results: Participants described paroxysmal events comprised of one or more symptoms. Symptoms included: ataxia, dysarthria, dystonia, oculomotor disorders, myoclonus/chorea, hypotonia, spasticity and tremors. The frequency, duration and functional impact of each movement disorder were variable. Informed by these findings, the diary was developed to assess the daily frequency, duration, type and functional impact of the heterogeneous paroxysmal movement disorders.

Conclusions: Developed in accordance with the FDA PRO Guidance (2009), the Glut1 DS Paroxysmal Movement Disorder Diary provides the first Glut1 DS-specific assessment of relevant paroxysmal movement disorders and their functional impact. Future qualitative and quantitative research will seek to confirm the content and psychometric validity of the instrument.

References: US Food and Drug Administration. Guidance for Industry: Patient Reported Outcome Measures: Use in Medical Product Development to Support Labeling Claims.  2009. http://www.fda.gov/downloads/Drugs/GuidanceComplianceRegulatoryInformation/Guidances/ucm071975.pdf

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MDS Abstracts - https://www.mdsabstracts.org/abstract/development-of-a-paroxysmal-movement-disorder-diary-for-patients-with-glucose-transporter-type-1-deficiency-syndrome-glut1-ds/