Depression in Alzheimer's disease patients: caregivers as surrogate reporters.

OBJECTIVE: To evaluate the use of caregivers as surrogate reporters of depressive symptoms in Alzheimer's disease (AD) patients on five depression measures.
DESIGN: Scale characteristics, including means, ranges, internal consistency, sensitivity, and item content of modified self-report questionnaire and interview depression measures were compared. PARTICIPANTS: Seventy-six patients, diagnosed with both depression and AD, and their family caregivers participated in this investigation. All subjects were community-residing participants in a treatment outcome investigation of behavioral treatment for depression. MEASUREMENTS: A Schedule for Affective Disorders and Schizophrenia (SADS) interview was completed on all subjects to establish a diagnosis of depression. Caregivers then completed three additional questionnaire measures about their patient: the Beck Depression Inventory (BDI), the Geriatric Depression Scale (GDS), and the Center for Epidemiological Studies-Depression Scale (CESD), all modified to provide a surrogate report of their patient's depressive symptoms. In addition, two interview measures were completed based on interviews with the caregiver and patient: the Hamilton Depression Rating Scale (HDRS) and the Cornell Scale for Depression in Dementia (CSDD).
RESULTS: Mean scores for this sample were above the recommended cutoff score for mild levels of depression on all measures. Coefficient alpha levels were comparable to levels reported for the traditional self-report formats. Sensitivity varied among the measures, with the CSDD most sensitive and the HDRS least sensitive. Item content varied across measures, particularly between questionnaire and interview measures.
CONCLUSIONS: Based on these results, it appears that caregivers are able to act as surrogate reporters of depression in AD patients. The modification of self-report questionnaires did not decrease their internal consistency, and they remained highly correlated with each other, supporting their validity when used in this manner. A two-step process of evaluating AD patients for depression is recommended: first, a surrogate report questionnaire completed by caregivers to screen patients, eliminating those who are unlikely to be depressed, and then a more extensive interview with those patients-and their caregivers- who appear likely to be depressed.