Cognitive testing in late-stage Parkinson's disease: A critical appraisal of available instruments.

Objective: For patients with Parkinson's disease (PD), cognitive impairment is one of the most disabling non-motor symptoms, particularly in the late disease stages (LSPD). Without a common cognitive assessment battery, it is difficult to estimate its prevalence and limits comparisons across studies. In addition, some instruments traditionally used in PD may not be adequate for use in LSPD. We sought to identify instruments used to assess cognition in LSPD and to investigate their global characteristics and psychometric properties to recommend a cognitive battery for the LSPD population.

Method: We conducted a literature search of EMBASE and MEDLINE for articles reporting the use of cognitive tests in LSPD. The global characteristics and psychometric properties of the four most used cognitive tests in each cognitive domain were verified to recommend a cognitive assessment battery.

Results: Of 60 included studies, 71.7% used screening scales to assess cognition. Of the 53 reported instruments, the Montreal Cognitive Assessment, the Digit Span, the Trail Making Test, the Semantic Fluency test, the Rey Auditory Verbal Learning Test, the Brief Visuospatial Memory Test-Revised, the Boston Naming Test, the Judgment of Line Orientation, and the Clock Drawing Test corresponded best overall to the requirements considered important for selecting instruments in LSPD.

Conclusion: Screening scales are frequently used to assess cognition in LSPD. We recommend a cognitive assessment battery that considers the special characteristics of the LSPD population, including being quick and easy to use, with minimized motor demands, and covering all relevant cognitive domains.