Aim: To test the psychometric attributes of the Scales for Outcomes in Parkinson's Disease-Cognition (SCOPA-Cog), in Castilian language.
Patients and methods: It is a multicenter, cross-sectional study carried out on 387 Parkinson's disease (PD) patients. They were 70% in Hoehn and Yahr stages 2 or 3; their mean age was 65,8 years and they underwent the disease for 8,1 years. Rater-based -SCOPA-Motor, modified Parkinson's Psychosis Rating Scale, Clinical Impression of Severity Index for PD (CISI-PD), Cumulative Illness Rating Scale-Geriatrics- and self-administered -SCOPA-Autonomic, SCOPA-Sleep, SCOPA-Psychosocial, Hospital Anxiety and Depression Scale, EuroQoL- assessments were applied. For SCOPA-Cog, the following psychometric attributes were analysed: acceptability, internal consistency, dimensionality, construct validity, and precision. A cut-off point for dementia and SCOPA-Cog score's predictors were explored.
Results: SCOPA-Cog was free from floor and ceiling effect. The internal consistency was satisfactory (alpha = 0,83) and the item-total correlation resulted equal or upper than 0,45. Two factors were identified (52% of variance), one of them formed by 3 out of the 4 memory-related items. The correlation with other measures was weak (rS < 0,35), except for the CISI-PD's item 'cognitive state' (rS = 0,51). SCOPA-Cog scored significantly different for Hoehn and Yahr stages and for patients grouped by age, age at onset of PD, and education. The standard error of measurement was 3,02. A cut-off point 19/20 reached 76% sensitivity and specificity for dementia. Age and age at onset of PD resulted the strongest predictors.
Conclusion: SCOPA-Cog is a consistent, valid, and precise measure for assessment of the cognitive disorder in PD.