Objective: The objective of this study was to compare the sensitivity, specificity, and diagnostic accuracy of the 15-item Geriatric Depression Scale (GDS-15) and the Hamilton Depression Rating Scale (HDRS) in patients with Parkinson disease (PD).
Method: A convenience sample of 148 outpatients with idiopathic PD receiving specialty care completed the GDS-15 and were administered the HDRS and Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (SCID) depression module by a research psychiatrist or trained research assistant. Receiver-operating characteristic (ROC) curves were plotted for the GDS-15 and HDRS scores with a SCID diagnosis of a depressive disorder as the state variable.
Results: Thirty-two subjects (22%) were diagnosed with a depressive disorder. The discriminant validity of the GDS-15 and HDRS were both high (ROC area under the curve: 0.92 and 0.91, respectively), with greatest dichotomization for the GDS-15 at a cutoff of 4/5 (87% accuracy, 88% sensitivity, 85% specificity) and the HDRS at a cutoff of 9/10 (83% accuracy, 88% sensitivity, 78% specificity).
Conclusions: The GDS-15 performs well as a screening instrument and in distinguishing depressed from nondepressed patients in PD. Its test characteristics are comparable to the HDRS. Because it is a brief instrument and can be self-administered, it is an excellent depression screening tool in this population.