Validation of the Italian version of Parkinson's disease-cognitive rating scale (PD-CRS)

Cognitive impairment (CI) is a frequent feature associated with both early and advanced stages of Parkinson's disease (PD). An evaluation of cognitive functions is relevant to identify those parkinsonians at risk of developing dementia. In the present study, the Italian version of Parkinson's Disease-Cognitive Rating Scale (PD-CRS) assessing fronto-subcortical and cortical cognitive functions in PD was validated in 387 parkinsonians and was used to test the empirical validity of the item 1.1 (cognitive impairment) of the Italian version of MDS-UPDRS as screening tool for CI in PD. PD-CRS was free from floor and ceiling effect. The mean PD-CRS score was 76.1 (mean cortical score, 24.5 ± 4.6; mean subcortical score, 51.5 ± 17.5). The internal consistency was satisfactory (α = 0.89); corrected item-total correlation was 0.570 (naming) to 0.696 (working memory). The correlation between PD-CRS and part I-IV of MDS-UPDRS was weak. The low agreement between classification of PD sample into patients with mild cognitive impairment (PD-MCI), dementia (PD-D) and normal cognition (PD-NC) according to scores of item 1.1 and classification according to cutoff scores of PD-CRS for PD-MCI, PD-D and PD-NC indicated a poor empirical validity of item 1.1 of MDS-UPDRS as cognitive screening tool for CI in PD (Κ = 0.114; weighted Κ = 0.17; SE of Κ = 0.038; 95 % confidence interval from 0.040 to 0.1895). The Italian version of PD-CRS is an easy, consistent and valid tool for assessment of the cognitive cortical and subcortical impairments in PD.