Reliability, validity, and diagnostic accuracy of Parkinson's Disease-Cognitive Rating Scale in Iranian patients with idiopathic Parkinson's disease

Abstract

Purpose To investigate the reliability and validity of Parkinson’s Disease-Cognitive Rating Scale (PD-CRS) in Iranian patients with idiopathic PD. Methods One hundred and eighty patients with PD and 60 age-, gender-, and educational level-matched healthy individuals participated in this study. Inter-rater and test–retest reliability of the Persian version of PD-CRS was investigated in 80 patients with PD. To evaluate the construct validity of the PD-CRS, its correlation with the Scales for Outcomes in Parkinson's disease-Cognition (SCOPA-Cog), Mini-Mental State Examination, Montreal Cognitive Assessment, Clock Drawing Test, Unified Parkinson’s Disease Rating Scale-Section I, and Quick Dementia Rating System was assessed. To assess the diagnostic accuracy of the PD-CRS, patients with PD were classified as groups with normal cognitive function, mild cognitive impairment (MCI), and dementia using the Clinical Dementia Rating. Results Test–retest and inter-rater reliability (ICC > 0.90), as well as internal consistency (α = 0.94) of the Persian version of PD-CRS, were excellent. A high positive correlation was found between the PD-CRS and SCOPA-Cog. A cut-off point of ≤79 (sensitivity 98.15% and specificity 98.04%) and ≤62 (sensitivity 100%, and specificity 100%) on the PD-CRS total score was obtained for detecting MCI and dementia in PD patients, respectively. Conclusions The results of this study showed that the Persian version of PD-CRS is a reliable and valid measure with high sensitivity and specificity to identify MCI and dementia in patients with PD. Implications for rehabilitation The PD-CRS has an excellent test–retest and inter-rater reliability and validity in Iranian patients with PD. The PD-CRS has high sensitivity and specificity for discriminating between different levels of cognitive impairment (i.e. no cognitive impairment, mild cognitive impairment, and dementia) in Iranian patients with PD.