Validation of the German Version of the Amsterdam Instrumental Activities of Daily Living Questionnaire®

Pretest:

Initially, five clinicians in the field will be asked to give feedback on the A-IADL-Q-SV German. Issues that need to be discussed include clarity of 1) answer options 2) the gradient of difficulty 3) activities or sentences. Adjustments will be made if necessary and documented.

At least five knowledgeable informants will then complete the A-IADL-Q-SV while thinking out loud and are asked to write down comments and issues on 1) the relevance of all items, 2) the applicability / meaning of the activities in Switzerland and 3) the understandability of the questions. The results will be reviewed in order to identify whether translation modifications will be necessary (e.g. rewording of items/response options). Additionally, the completed questionnaires will be explored to detect high proportions of missing items or single responses. If adjustments will be made, they will be discussed with the developer to finalize the translated German version.

Validation:

The A-IADL-Q-SV German will be tested in the community (people with normal cognition)and three memory clinic settings (people with MCI, mild dementia) including a total of 100 informants from people with normal cognition, MCI and mild dementia.

Construct validity will be assessed whether the A-IADL-Q-SV German shows the expected correlations with the mini mental state examination (MMSE), the cumulative dementia rating (CDR), the Lawton Brody Scale, the IQCODE and the Depression im Alter scale (DIA-S) Internal consistency will be assessed using item response theory (IRT) by investigating whether the translated version fits the graded response model of the original version and whether the assumptions of IRT are still met (unidimensionality, local independence and monotonicity).

Measurement invariance will be investigated using IRT by investigating whether differential item functioning is present in the comparison of the item characteristic curves of the original and translated version.

Responsiveness will be examined whether the A-IADL-Q-SV is able to discriminate people with MCI from people with normal cognition/ mild dementia Test-Retest reliability will be assessed on item level

Inclusion criteria

• Living in the community
• Ability to understand the purpose of the study and to consent
• Knowledgeable informant available
• Signed informed consent to participate in the study

Exclusion criteria

• Moderate and severe cognitive decline (MMSE < 20) (people with MCI, mild dementia)
• Cognitive decline suspect based on telephone screening (people with normal cognition)
• Cognitive decline due to other causes than Alzheimer's disease, vascular dementia (e.g. neurological diseases, trauma, delirium)
• Diagnosed Depression
• Diagnosed Alcohol or Drug Misuse