Development of Clinical Dementia Rating Scale Cut-off Scores for Patients With Parkinson's Disease

Background: The aim of this study was to explore validity of the Clinical Dementia Rating Scale (CDR) in measuring cognitive impairment among individuals with Parkinson's disease (PD). The scale was created for use in patients with Alzheimer's disease, and, to date, there have been no published studies examining whether this tool is appropriate for patients with PD. Methods: The data were obtained from the National Alzheimer's Coordinating Center database and included 490 subjects diagnosed with PD, further categorized as having PD dementia (n = 151), mild cognitive impairment (n = 186), or normal cognition (n = 153) by a treating physician. Sensitivity, specificity, positive predictive value, and negative predictive value were calculated for the CDR Scale Global Score as well as the Sum of Boxes Score using existing cut-off scores. Finally, new cut-off scores were calculated using sensitivity and specificity values derived using receiver operating characteristic curves. Results: Sensitivity and specificity of the published Global Score cut-off scores for patients with dementia were 0.34 and 0.10, respectively. The newly calculated cut-off scores for patients with dementia yielded a sensitivity of 0.79 and a specificity of 0.96. The area under the curve was 0.92 (95% confidence interval = 0.90-0.95). Conclusion: The CDR is a useful tool in identifying dementia in patients with PD when the cut-off scores are adjusted.