Objective: Develop a patient-reported outcome (PRO) modification of the Functional Rating Scale for pre-Huntington Disease (FuRST-pHD) using focus group, Delphi panel and cognitive pre-testing methodology.

Background: The FuRST-pHD was developed as a clinician-rated outcome to assess functional ability in premanifest and early-manifest Huntington’s disease (Vaccarino et al., 2011). Examination of the scale’s clinimetric properties revealed multiple deficiencies including usability issues, potential floor effects, low levels of internal consistency and poor content validity. We sought to develop a modified scale to be completed by respondents with acceptable levels of usability, reliability, and content validity.

Methods: We employed standard rating scale development methodology to identify domains of interest for functional assessment in HD and potential items to assess those domains. Data from 6 focus groups comprising premanifest HD (n=35), early-manifest HD (n=27) and companions (n=41) were evaluated using framework analyses. These data were used by a group of 13 international HD experts (Delphi panel) to identify the most important domains of interest using a Content Validity Ratio (CVR) statistic and draft potential items used to assess these domains. These items were administered to 20 premanifest HD gene-expansion carriers (HDGECs) and 15 of their companions, and 20 early-manifest HDGECs and 20 of their companions for qualitative analyses using cognitive pretesting methods. We investigated the ease of comprehension of instructions, items and scoring and respondents’ comfort with the items.

Results: Framework analyses of the focus group data revealed a list of 27 concerns identified by HDGECs and their companions. From this list, the Delphi panel developed a list of 18 domains that met the CVR criterion and designated a 5-point standardized Likert-type scale in a PRO format applied to 22 potential items. These items were used for cognitive pretesting and minor issues were identified for the individual items.

Conclusions: The process of focus group analysis, Delphi panel deliberations and cognitive pretesting were used successfully to develop a revised version of a PRO functional assessment for use in premanifest HD. Final validation of the modified FuRST-pHD will be conducted in a large international cohort of study participants.

References: Vaccarino AL, Sills T, et al. Assessment of cognitive symptoms in prodromal and early Huntington disease. PLoS currents. 2011 Oct 25;3.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/furst2-0-development-of-a-modified-functional-rating-scale-for-use-in-premanifest-and-early-manifest-huntingtons-disease/