The National Task Group on Intellectual and Developmental Disabilities Practices (NTG) developed a screening tool called the NTG - Early Detection Screen for Dementia (NTG-EDSD). This questionnaire was created for family members, caregivers, and agencies to use "for the early detection screening of those adults with an intellectual disability who are suspected of or may be showing early signs of mild cognitive impairment or dementia."
Additional information and links to download the screening tool in several languages can be found at this link: www.the-ntg.org/ntg-edsd.
