How cautious should we be when assessing apathy with the Unified Parkinson's Disease Rating Scale?

Current practice often assesses apathy with a single item from the Unified Parkinson's Disease Rating Scale (UPDRS, item 4). Yet, the relationship between the UPDRS item 4 and the validated Apathy Scale (AS) is unknown. The purpose of this study was to evaluate the operating characteristics of UPDRS item 4 in relation to the AS. Three hundred and one patients with PD were administered the AS and the UPDRS. We compared the UPDRS item 4 to the standard AS classification of > or =14 as apathetic. A receiver operating characteristics (ROC) curve was obtained, and sensitivity, specificity, positive, and negative predictive power were calculated. The ROC curve showed area under the curve as 0.75. A cut-off of 1 had good sensitivity (81%) but poor specificity (53%; high false positive rate). A cut-off point of 2 had acceptable specificity (87%) but poor sensitivity (52%, high false negative rate). Continuing to increasing the cut-off point (e.g., 3, 4) continues to increase specificity at the expense of dramatically reducing sensitivity. These findings suggest the use of caution when screening for apathy with item 4 due to its poor sensitivity in relation to the AS.