Total functioning capacity scale in Huntington's disease: natural course over time

Area of Science:

• Neuroscience
• Genetics
• Clinical Research

Background:

• The Total Functioning Capacity (TFC) assessment is crucial for monitoring Huntington's disease (HD) progression in research and clinical settings.
• Understanding the natural course of functional decline and improvement in HD is essential for effective trial design and patient care.

Purpose of the Study:

• To investigate the natural progression of functional capacity in individuals with Huntington's disease (HD).
• To analyze how age and CAG-repeat length influence changes in Total Functioning Capacity (TFC) scores.
• To evaluate the strengths and limitations of the TFC assessment in longitudinal HD studies.

Main Methods:

• Analysis of clinical data from the Enroll-HD platform (version 5, including Registry-3) involving 21,079 participants.
• Focus on 15,527 participants with 52,457 visits and TFC scores ranging from 0 to 13.
• Examination of TFC score changes over time in relation to age and CAG-repeat length.

Main Results:

• Most individuals maintained maximum functional capacity; however, 3505 participants experienced TFC score changes.
• Within 4 years, 64.1% of those with changing scores declined, while 18.6% improved.
• Age-related functional decline followed a sequence: occupation, finances, daily living, and care needs; longer CAG repeats correlated with earlier decline.

Conclusions:

• A substantial number of Huntington's disease patients show regained functional capacity, highlighting TFC's utility despite potential interrater variability.
• The TFC assessment accurately reflects intended changes across functional domains in HD.
• Analysis of the reduced penetrance group suggests potential biases in healthcare-seeking behavior unrelated to HD progression.