Evaluation of a screening instrument for dementia in ageing mentally retarded persons.

The value of a standardized hetero-anamnestic questionnaire, the Dementia Questionnaire for Mentally Retarded Persons (DMR), as a screening instrument for diagnosis of early dementia, has been evaluated during a longitudinal follow-up of 139 institutionalized ageing mentally retarded subjects. By means of decision analysis, provisional criteria have been derived for a diagnosis, based on absolute DMR scores and on scorechanges through time. For different intellectual levels, separate criteria are required for interpretation of absolute scores, but longitudinal scorechanges might be independent of the intellectual level. The DMR was only evaluated for the mildly and moderately retarded intelligence categories, because of the small number of dementing persons among the severely and profoundly retarded subjects. Causes of false-positivity and false-negativity are considered.