Staging of cognitive impairment in Parkinson's disease: validity of Quick Dementia Rating System

Purpose: This study aimed to investigate the ability of the Quick Dementia Rating System (QDRS) to discriminate patients with PD who have mild cognitive impairment from those without cognitive impairment and those with dementia. Method: A total of 105 patients with PD were classified as without cognitive impairment (N = 32), with mild cognitive impairment (N = 23), and PDD (N = 50), according to their score on clinical dementia rating. Multivariate regression analysis was performed considering age, education, and disease severity as covariates and mild cognitive impairment or dementia as outcome variables. Receiver operating characteristic curve analysis was carried out to derive the optimal cut-off points. Results: The cut-off point >2.5 (sensitivity = 86.96%, area under curve (AUC) = 0.88) was obtained for discriminating patients with mild cognitive impairment from those without cognitive impairment based on the total score of QDRS. The cut-off point >5 (sensitivity = 84%, AUC = 0.84) was derived for discriminating mild cognitive impairment from dementia based on the total score of QDRS. Conclusions: The results of this study showed a good discriminative validity of the QDRS for discriminating mild cognitive impairment from no cognitive impairment and dementia in patients with PD.