Measuring Dementia Knowledge in German: Validation and Comparison of the Dementia Knowledge Assessment Scale, the Knowledge in Dementia Scale, and the Dementia Knowledge Assessment Tool 2

Background: Assessing dementia knowledge is critical for developing and improving effective interventions. There are many different tools to assess dementia knowledge, but only one has been validated in German so far. Objective: To validate two tools for assessing dementia knowledge - the Dementia Knowledge Assessment Scale (DKAS-D) and the Knowledge in Dementia Scale (KIDE-D) for the German general population - and compare their psychometric properties with the Dementia Knowledge Assessment Tool 2 (DKAT2-D). Methods: A convenience sample of 272 participants completed online surveys. Analyses included internal consistency, structural validity, construct validity through the known-groups method, retest-reliability with a subgroup of n = 88, and floor and ceiling effects. This study used the STROBE checklist. Results: Internal consistency was acceptable for DKAT2-D (alpha = 0.780), very good for DKAS-D (alpha = 0.873), and poor for KIDE-D (alpha = 0.506). Construct validity was confirmed for all questionnaires. Retest-reliability was good for DKAT2-D (0.886; 0.825-0.926) and KIDE-D (0.813; 0.714-0.878), while it was great for DKAS-D (0.928; 0.891-0.953). Trends toward ceiling effects were observed for DKAT2-D and KIDE-D but not for DKAS-D. The principal component analysis did not reveal a coherent structure for DKAT2-D or KIDE-D, while the confirmatory factor analysis proposed the removal of 5 items for DKAS-D, resulting in the shortened DKAS20-D, which had nearly identical properties. Conclusion: Both DKAS-D and its shortened version, DKAS20-D, are reliable instruments for evaluating programs intended for the general population, as they were found to be convincing in all aspects.