DEVELOPMENT OF CLINICAL DEMENTIA RATING SCALE CUTOFF SCORES FOR PATIENTS WITH PARKINSON'S DISEASE.

BACKGROUND: The purpose of this study was to explore validity of the Clinical Dementia Rating Scale in measuring cognitive impairment among individuals with Parkinson's disease. The scale was created for use in patients with Alzheimer's disease and, to date, there have been no published studies examining if this tool is appropriate for patients with Parkinson's disease.

METHODS: The data were obtained from the National Alzheimer's Coordinating Center database and included 490 subjects diagnosed with Parkinson's disease, further categorized as having Parkinson's disease 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 values were calculated for the Clinical Dementia Rating Scale Global Score as well as the Sum of Boxes Score using existing cutoff scores. Finally, new cutoff scores were calculated using sensitivity and specificity values derived using Receiver Operating Characteristic curves.

RESULTS: Sensitivity and specificity of the published Global Score cutoff scores for patients with dementia were .34 and .10, respectively. The newly calculated cutoff scores for patients with dementia yielded a sensitivity of .79 and a specificity of .96. The area under the curve was 0.92 (95% CI = 0.90-0.95).

CONCLUSION: The CDR is a useful tool in identifying dementia in patients with Parkinson's disease when the cutoff scores are adjusted.