Measuring cognition in a geriatric outpatient clinic: Rasch analysis of the Montreal Cognitive Assessment.
OBJECTIVE
To evaluate the psychometric properties of the Montreal Cognitive Assessment as a quantitative measure of cognitive ability.


METHODS
A total of 222 cases extracted from a clinical database (57-91 years) of patients screened for cognitive impairment in outpatient geriatric assessment clinics.


METHODS
Demographic information and individual item responses to Montreal Cognitive Assessment.


RESULTS
Comparison of the data with a unidimensional Rasch model indicated that the total score obtained by summing across all items yields a reliable (0.75) quantitative estimate of global cognitive ability. All items fit the model and together spanned a range of difficulty from -3.75 to +2.88 logits. Items were assessed for differential item functioning across such patient characteristics as age, education, and language spoken. We provide a table for converting Montreal Cognitive Assessment total scores onto a linearly scaled score, with guidelines for interpreting changes in Montreal Cognitive Assessment score in terms of their statistical significance.


CONCLUSIONS
The Montreal Cognitive Assessment can provide a reliable and valid quantitative estimate of cognitive ability in a geriatric cognitive disorders clinic setting.
Koski
Lisa
L
Divisions of Geriatrics and Clinical Epidemiology, Faculty of Medicine, McGill University, and the Research Institute of the McGill University Health Centre, Montreal, Quebec, Canada. lisa.koski@mcgill.ca
Xie
Haiqun
H
Finch
Lois
L
D000368:Aged; D000369:Aged, 80 and over; D000375:Aging; D000554:Ambulatory Care Facilities; D003071:Cognition; D003072:Cognition Disorders / Q000175:diagnosis; D016208:Databases, Factual; D004493:Education; D005260:Female; D015577:Geriatric Assessment / Q000379:methods*; D006757:Hospital Units; D006801:Humans; D007802:Language; D008297:Male; D008875:Middle Aged; D008962:Models, Theoretical; D009483:Neuropsychological Tests; D011594:Psychometrics