ABSTRACT
OBJECTIVE: Data in the literature show different estimates of the prevalence of depression in patients with Alzheimer disease (AD) when different classification systems are used. This study describes the prevalence and clinical features of depression in AD based on five different depression classification systems. METHODS: This was a cross-sectional, observational study of 491 patients with probable AD. Depression was diagnosed using five classification systems (International Classification of Diseases, 10th Revision [ICD-10], Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition [DSM-IV], Cambridge Examination for Mental Disorder of the Elderly [CAMDEX], Provisional Diagnostic Criteria for depression in AD [PDC-dAD], Neuropsychiatric Inventory [NPI]). RESULTS: The prevalence of depression was 4.9% (95% confidence interval [CI]: 3.2-7.1) according to ICD-10 criteria; 9.8% (95% CI: 7.3-12.6) according to CAMDEX; 13.4% (95% CI: 10.6-16.6) according to DSM-IV; 27.4% (95% CI: 23.6-31.5) according to PDC-dAD criteria; and 43.7% (95% CI: 39.4-48.2) when using the screening questions from the NPI depression subscale. The level of agreement between the classification systems was low to moderate (kappa <0.52). The characteristics associated with the most diagnostic disagreement were loss of confidence or self-esteem and irritability. CONCLUSIONS: This study shows that there is a high variability in the prevalence rates of depression in AD depending on the diagnostic criteria used and that there is a low rate of agreement among the diagnostic criteria analyzed. The results suggest that the use of generic diagnostic criteria such as the ICD-10, the CAMDEX, or DSM-IV provides low prevalence rates of depression in patients with AD compared with specific diagnostic criteria such as the PDC-dAD.
