French-English cross-linguistic comparison and diagnostic impact of the AD-8 dementia screening questionnaire in a geriatric assessment clinic.

The AD-8 dementia screening questionnaire is a novel tool that allows clinicians to assess changes in cognitive function. This study examined psychometric properties of the test in French-speaking and English-speaking patients, and its impact on diagnostic practice in the geriatric assessment clinics of a university health centre. Data were extracted from the clinical database for all new patients screened for cognitive impairment 15 months before (historic control group) and 15 months after the introduction of the test (AD-8 group and concurrent control group). Analysis of differential item functioning revealed formal equivalence of the French- and English-language items, supporting the validity of the French version. Respondent type significantly influenced the total score on the AD-8. Concurrent validity with other cognitive screening tests was moderately high. Finally, among patients who did not present with pre-existing dementia, a higher proportion of dementia diagnoses was made in those administered the AD-8 relative to the concurrent control group. Implications for clinical use of the AD-8 are discussed. 2010 S. Karger AG, Basel.