Reliability of psychiatric scales in patients with dementia of the Alzheimer type.

For 43 patients with probable Alzheimer's disease who were screened for psychiatric disorders, the interrater reliability of the Global Deterioration Scale, BPRS, and Hamilton Rating Scale for Depression was high (intraclass correlation, 0.82-0.998). As expected, the prevalence of psychiatric symptoms in this sample was low. The score on the Zung Self-Rating Depression Scale correlated with the score on the rater-administered Hamilton depression scale in patients whose Alzheimer's disease was of low severity (N = 24) but not high severity (N = 19).