Objective: To evaluate the response options on the FuRST 2.0 measure of HD functional ability.

Background: FuRST 2.0 is a PRO created to detect changes in functional ability in HD‑ISS stage 2 and mild stage 3 developed using scale development methodology of focus groups, Delphi panels, and multiple rounds of cognitive debriefing. Based on qualitative research and informal regulatory feedback we selected the following 5 response options: Never did this activity (NDT), No, Mild, Moderate, or Severe functional difficulty.  For response symmetry and ease of reading the same 5 response options were used for each of the 24 scale items. Large-scale validation studies are being conducted in FOCUS-HD, a series of on-line and in-person studies.

Method: We examined the frequency of the response option NDT in 765 people with HD (PwHD) HD-ISS 2 and mild 3 from the Enroll-HD study, a longitudinal observational HD study.  The HD sample had mean scores (SD) of Total Motor Score 15.4 (15.8), Total Functional Capacity 11.6 (1.9), and FuRST 2.0 8.9 (10.0).

Results: There were 263 respondents who selected NDT with individual item endorsement rates from 1 to 12.  Items with the highest endorsement rate for NDT include sexual activities (144), doing job (98), driving (73), and exercising (67), but some respondents endorsed NDT this on items that don’t make sense; speech (12), controlling temper (9), and sleeping (6).

Conclusion: If a respondent selects NDT at baseline (score of 0) and then endorses mild (score of 1), moderate (2) or severe (3) at follow up, it may appear the participant is worse, as the FuRST 2.0 total score is higher. It is possible that at baseline the respondent did not attempt the activity due to HD symptoms. Thus, attempting the activity is a sign of improvement.  Furthermore, endorsing NDT when it is implausible introduces significant measurement concerns and the NDT endorsement frequency across multiple items is problematic for longitudinal studies, including clinical trials.  Studies are underway to better understand why respondents select the NDT response. Additionally, alternative scoring approaches and the removal of the NDT as a response option are being considered. Scale developers should be cautious about using a NDT response option unless it serves a clear, pre-specified purpose and can be interpreted consistently.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/furst-2-0-a-patient-reported-outcome-pro-measure-of-functional-ability-in-huntingtons-disease-hd-getting-response-options-right/