Objective: To develop a patient/care giver-reported scale that is capable of assessing functional disability in CBD that can be easily and reliably used in clinical and research settings. 

Background: CBD is an adult-onset 4R tauopathy presenting with several possible overlapping motor, behavioral, language and cognitive clinical phenotypes. No available clinical rating scale is capable of evaluating the the functional impact of the multifaceted and changing nature of this complex disorder particularly in the context of disease modifying treatment trials. 

Methods: Committees of movement disorders and behavioral neurologists (7 members each) with considerable experience in CBD first formally reviewed recently proposed diagnostic criteria for CBD and FDA documentation on the development of patient reported outcome measures for clinical trials. They then reviewed individual items from selected validated motor and behavioral scales in light of the various features of CBD regarding relevance to CBD, ease of application, availability of alternative validated measures and missing factors not adequately assessed. Functional domains (62) and specific symptoms (36) were rated with respect to importance and contribution to patient’s functional ability and a large number of potential scale items were developed accordingly. This was followed by a multi-staged modified Delphi exercise requiring each committee member to rate scale items for overlap and relevance and rank them in order of perceived importance to CBD eventually providing each item’s content validity ratio. The resultant scale then underwent staged cognitive pretesting to assess task difficulty for both examiners and respondents (patients and caregivers) with subsequent editing of scale items to address arising concerns.

Results: The resultant working version of the CBD-FS is composed of Motor Experiences in Daily Living (12 items), Language/Cognitive/Behavioral (13 items) and Other Non-Motor Experiences of Daily Living (6 items) components (Table). This version is currently being used in participating clinics to determine ease of application and will be validated against other rating scales in existing and upcoming research projects of 4R tauopathies.

Conclusions: A reliable and valid CBD-FS will serve as an ideal primary outcome measure in future trials of this complex disorder and will also be useful in the study of related frontotemporal degenerations.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/the-corticobasal-degeneration-functional-rating-scale-cbd-fs/