The Parkinson's Disease-Cognitive Rating Scale (PD-CRS): normative values from 268 healthy Italian individuals

The Parkinson's Disease-Cognitive Rating Scale (PD-CRS) is a cognitive screening battery that includes subtests to assess cortical and subcortical functions. It is a valid screening tool for mild cognitive impairment (MCI) in Parkinson's disease (PD) and is recommended for diagnosing PD-MCI-Level I. Until now, no study has provided population-based norms for the Italian population. The aim of the present study was to collect normative values in a sample of Italian healthy subjects. Two hundred and sixty-eight (125 men) participants of different ages (age range 30-79 years) and educational levels (from primary school to university) underwent the PD-CRS. Regression-based norming was used to explore the influence of demographic variables (age, education level, and gender) on PD-CRS total score, frontal-subcortical and instrumental-cortical sub-scores, and score achieved on each task of the PD-CRS. Multiple linear regression analysis revealed that age and education significantly predicted the total score, the two sub-scores and the score on each task of the PD-CRS. No significant effect of gender was found. From the derived linear equations, a correction grid for raw scores was developed. Inferential cut-off scores, estimated using a non-parametric technique, were 71.25 for PD-CRS total score and 46.25 and 20.17 for frontal-subcortical and instrumental-cortical sub-score, respectively. Since the use of adjusted scores is more informative when they are standardized, we have converted adjusted scores into equivalent scores. The present study provides normative data for the PD-CRS, being useful and recommended by Movement Disorders Society task force to identify PD-MCI-Level I, at several stages of the disease.