The validity of the Beck Depression Inventory as a screening and diagnostic instrument for depression in patients with Parkinson's disease

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Abstract
PURPOSE To evaluate the validity of the Beck Depression Inventory (BDI) as a screening and diagnostic scale for depression in Parkinson's disease (PD). PATIENTS AND METHODS Fifty‐three nondemented patients with PD were diagnosed according to a standardized protocol consisting of the depression module of the Structured Clinical Interview for DSM axis I disorders (SCID) and the BDI. A “receiver operating characteristics” (ROC) curve was obtained and the sensitivity, specificity, positive and negative predictive values (PPV and NPV, respectively) were calculated for different cut‐off points of the BDI. RESULTS Maximum discrimination was obtained with a cut‐off score of 13/14. High sensitivity and NPV were obtained with cut‐off scores of 8/9 or lower; a high specificity and PPV were obtained with cut‐off scores of 16/17 or higher. The area under the ROC curve was 85.67%. CONCLUSION A single cut‐off score on the BDI to distinguish nondepressed from depressed patients with PD is not feasible. If one accepts the low specificity, then the BDI can be used as a valid screening instrument for depression in PD with a cut‐off of 8/9. With a cut‐off score of 16/17, it can be used as a diagnostic scale, at the cost of a low sensitivity. The use of diagnostic criteria for depression remains necessary.