Informant-based Assessment Instruments for Dementia in People with Intellectual Disability: A Systematic Review and Standardised Evaluation

Dementia in people with intellectual disability (ID) is frequent but hard to recognise. Evidence-based recommendations for suitable instruments are lacking. The present study set out to evaluate informant-based dementia assessment instruments and to provide evidence-based recommendations for instruments most suitable in clinical practice and research. A systematic review was conducted across ten international electronic databases. The COnsensus-based Standards for the selection of health Measurement INstruments (COSMIN) guidelines, including a risk of bias assessment, was applied to extract information and to evaluate measurement properties and the quality of available evidence. In total, 42 studies evaluating 18 informant-based assessment instruments were analysed. For screening purposes, we recommend the Behavioral and Psychological Symptoms of Dementia in Down Syndrome Scale (BPSD-DS), the Cognitive Scale for Down Syndrome (CS-DS), the Dementia Screening Questionnaire for Individuals with Intellectual Disabilities (DSQIID), and provisionally the NTG-EDSD. For a more thorough dementia assessment, we recommend the Cambridge Examination for Mental Disorders of Older People with Down's Syndrome and Others with Intellectual Disabilities (CAMDEX-DS). Our study informs clinicians and researchers about adequate, well-evaluated dementia assessment instruments for people with ID, and highlights the need for high quality studies, especially regarding content validity.