Development and validation of a brief observer-rated screening scale for depression in elderly medical patients

Abstract

Objective: to develop a depression screening scale that does not rely on verbal communication. Setting: an acute geriatric unit in a teaching hospital. Subjects: 96 patients (mean age 81 years, range 68-92, 59 women); 40% of the initial study group of 50 and 22% of the validation group of 46 were diagnosed as depressed. Methods: we devised a scale using nine items which could be rated by an observer; we determined inter-rater reliability, sensitivity, specificity and predictive values for each item compared with a Geriatric Mental State-AGECAT diagnosis of depression; we validated a final scale of six items. Results: inter-rater reliability was poor for two items (irritability and sleep disturbance) while two items (sleep disturbance and night sedation) had poor sensitivity; we omitted these items in a revised scale. Re-analysis of data from the initial study showed that a cut-off of ≥ 3 on the revised scale gave a sensitivity of 83%, a specificity of 95%, a positive predictive value of 0.89 and a negative predictive value of 0.90. Spearman's correlation coefficient between the six-item questionnaire and the Hamilton rating scale was 0.79. In the validation study, the cut-off score of ≥ 3 on the revised six-item scale had a sensitivity of 90%, specificity of 72%, a positive predictive value of 0.69 and a negative predictive value of 0.96. Conclusions: this simple, short, observation-based screening scale completed by nurses is sensitive and specific in identifying depression in elderly medically ill patients, and may be a useful addition to clinical practice.