Objective: To empirically evaluate the psychometric properties of the 15-item Geriatric Depression Scale (GDS-15); determine the optimal cutoff points and screening performance for the detection of major depression; and examine differential item functioning (DIF) to determine the variability of item responses across sociodemographics in an elderly home care population.
Design: A secondary analysis of data collected from a random sample study.
Setting: Homebound subjects newly admitted over a 2-year-period to a large visiting nurse service agency in Westchester, New York.
Participants: Five hundred twenty-six subjects over age 65, newly admitted to home care for skilled nursing.
Measurements: Major depression was diagnosed using both patient, Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, and best estimate procedures. Self-report measures included the GDS-15, activities of daily living (ADL), instrumental ADL, and pain intensity. Cognitive impairment was assessed using the Mini-Mental State Examination and medical morbidity using the Charlson Comorbidity Index.
Results: Optimal cutoff (5) yielded sensitivity 71.8% and specificity of 78.2%, however, the accuracy of the GDS-15 was not influenced by severity of medical burden. Persons with a cluster of ailments were twice as likely (Adj odds ratio = 2.47; 95% confidence interval = 1.49-4.09) to be diagnosed with depression. DIF analyses revealed no variability of item responses across sociodemographics.
Conclusion: Main findings suggest that the accuracy of the GDS-15 was not influenced by severity of clinical or functional factors, or sociodemographics. This has broad implications suggesting that the very old, ill, and diverse populations can be appropriately screened for depression using the GDS-15.