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Background: The USA National Task Group (NTG) guidelines advocate the use of an adapted version of Dementia Screening Questionnaire for Individuals with Intellectual Disabilities (DSQIID) for dementia screening of individuals with Down syndrome (DS) and with other forms of ID (non-DS). Objective: In order to meet these guidelines, this study verifies the psychometric properties of an Italian version of the original DSQIID in a population composed of adults aged 40 years and over with DS and non-DS ID. Methods: Internal consistency, inter-rater and intra-rater reliabilities, structural validity, convergent validity and known group differences of DSQIID-I were assessed with 200 individuals with ID (mean of 55.2 years; range: 40-80 years) recruited from 15 different centers in Italy. Diagnosis of dementia was done according to IASSID diagnostic criteria and its degree of clinical certainty was defined according to Silverman et al.'s classification (2004). Results: Cronbach's alpha for the DSQIID-I was 0.94. The ICCs for inter-rater and test-retest reliability were both 0.89. A Principal Component analysis revealed three domains, namely memory and confusion- related items, motor and functional disabilities, depression and apathy, which explained almost 40% of the overall variance. The total DSQIID-I score correlated significantly with DMR and differed significantly among those individuals (n = 34) with cognitive decline from those without (n = 166). Age, gender and severity of ID were unrelated to the DSQIID-I. Conclusion: The present study confirms the cross-cultural value of DSQIID which was proved to be a psychometrically valid and user-friendly observer-rated scale for dementia screening in adults with both DS and non-DS ID.

The evaluation of a patient’s mental state, overall clinical profile and behavioural disturbance in the process of diagnosing dementia requires at least two sources of information: the patient and the informant. Since the severity of the dementia may interfere with the subjective perception of these disorders, it is important to evaluate the consistency between these two sources of information and the clinical and psychometric evaluation made by the physician. Accordingly, in this study five behavioural areas, derived from the semi-structured interview schedule provided by the Cambridge Examination for Mental Disorders of the Elderly (CAMDEX, i.e., Sleep, Depressed Mood, Everyday Activity, Memory and Global Mental Functioning) have been tested on the patient and his/her informant. Eighty dementia patients (mean age = 74 years) and their informants participated in the study. The dementia group was subdivided into two levels of severity according to DSM-IIIR criteria: 41 with milddementia and 39 with moderatedementia, respectively, matched for age and schooling. The rating of impairment was found to increase along with the severity of dementia in all the above-mentioned areas, except for sleep. However, the source of information per sesignificantly influenced the evaluation of memory functioning. Moreover, the significant interaction between the two factors considered indicates that memory functioning is evaluated quite differently by the patients and the informants, as only in the assessment made by the latter group did the impairment increase in parallel with severity of dementia. Finally, whereas none of the subjective measures recorded in the patients were significantly correlated with their test scores, the correlations between the informant memory appraisals and patient test results proved to be significant. The present findings confirm the validity of informant reports in assessing cognitive and memory disorders in early-stage dementia, as well as in distinguishing patients with mildfrom those with moderatedementia.