This diagnostic aid has been developed to identify dementia-related changes in people with severe/profound intellectual (and multiple) disabilities - abbreviated as SPI(M)D - and it can be used in the diagnostic process. The results of the diagnostic aid only are not sufficient to make a diagnosis. Changes can also be caused by other conditions with dementia-like symptoms. These potential differential diagnoses must be ruled out.The diagnostic aid consists of two parts. The first part asks general information about the interviewer, informant(s), and the person with SPI(M)D. The second part contains 42 items on dementia-related changes, categorized into seven symptom domains. For each item, it is asked whether a change has been observed in the last six months compared to the typical/characteristic functioning or behaviour. This refers to the functioning or behaviour that is typical of the person and that they have exhibited during adult life before deterioration occurred.1. Changes in cognition2. Changes in language and speech3. Behavioural changes4. Changes in eating and drinking5. Changes in personal care6. Changes in motor skills7. Additional health problemsThe collection protocol is described in detail in the accompanying manual. The manual must be followed carefully.