Differentiating between demented and psychiatric patients with the Dutch version of the IQCODE

This study presents psychometric data on the Dutch version of the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE-N). We focused on differentiating between inpatients with dementia or a mood/psychotic disorder. A cutoff point of 3.9 on the IQCODE-N correctly predicted group membership in 87.8% and 78.8% respectively. Internal consistency and principal component analysis suggest that the IQCODE-N measures a unidimensional construct. Correlations with a Dementia Screening Test (r = 0.62), nurses' observations on memory disorders (r = 0.71) and a global assessment of severity of dementia (r = 0.72) support the validity of the informant ratings. Patients' age and level of education did not confound informant ratings. Only a small fraction of the informants could not complete the IQCODE-N, which makes it an easily applicable rating scale for cognitive decline.