Background: Outcome measures that capture functional abilities related to cognition offer the potential to demonstrate real‐world effectiveness of cognitive‐enhancing treatments. However, distinguishing functional disability related to cognition from that attributed to motor symptoms can be difficult in PD. A performance‐based functional assessment allows for direct observation of activity of daily living skills and separation of cognitive from motoric disabilities.
Objectives: Validate the University of California San Diego Performance‐Based Skills Assessment in PD.
Methods: One hundred PD participants, ranging from normal cognition to dementia, completed the University of California San Diego Performance‐Based Skills Assessment, a performance‐based measure of cognitively demanding activities of daily living, as well as a neuropsychological battery and motor examination. Cognitive classification was determined by consensus conference, blinded to University of California San Diego Performance‐Based Skills Assessment scores. Psychometric properties of the University of California San Diego Performance‐Based Skills Assessment, including internal consistency, test‐retest and inter‐rater reliability, and discriminant validity for dementia, were examined.
Results: The University of California San Diego Performance‐Based Skills Assessment demonstrated strong internal consistency (Cronbach's α = 0.82) and test‐retest reliability (r = 0.89) and correlated strongly with global cognition (Mattis Dementia Rating Scale: r = 0.80; P < 0.001). University of California San Diego Performance‐Based Skills Assessment regression models indicated greater contribution from cognitive explanatory variables (marginal partial: R2 = 0.33) than motor variables (marginal partial: R2 = 0.05), controlling for age, education, disease duration, and l‐dopa equivalent dose. Additionally, the University of California San Diego Performance‐Based Skills Assessment exhibited strong discriminant validity for dementia (area under the curve = 0.91).
Conclusions: The University of California San Diego Performance‐Based Skills Assessment is a valid measure of functional abilities related to cognition rather than motor symptoms in PD. Furthermore, it reliably distinguishes demented from nondemented participants. The University of California San Diego Performance‐Based Skills Assessment may be considered as an outcome measure that combines cognitive and functional abilities in treatment trials for cognitive impairment in PD. © 2018 International Parkinson and Movement Disorder Society