Assessment of psychiatric complications in Parkinson's disease: The SCOPA-PC.

The objective of this study was to develop a clinimetric sound scale that addresses both psychotic and compulsive complications in Parkinson's disease (PD). The SCales for Outcomes in PArkinson's disease-Psychiatric Complications (SCOPA-PC) was developed by modifying the items of the Parkinson Psychosis Rating Scale (PPRS) and including an item on compulsive behavior in PD. To evaluate the validity of the SCOPA-PC, 106 PD patients were assessed. A subsample of 43 patients was assessed for interrater and test-retest reliability. Construct validity was evaluated using the Neuropsychiatric Inventory (NPI) and the South Oaks Gambling Scale (SOGS). Interrater and test-retest reliability for the total score was 0.95 and 0.91 (intraclass correlation coefficient), respectively. For the items, the interrater reliability ranged from 0.62 to 0.96 (weighted kappa) and the test-retest reliability ranged from 0.54 to 0.88 (weighted kappa). Cronbach's alpha was 0.68. The correlation between the SCOPA-PC total score and the NPI was 0.41. The correlation between SCOPA-PC items and NPI items that addressed similar constructs ranged from 0.34 to 0.68, whereas the correlation between the item on compulsive behavior and the SOGS was 0.49. In conclusion, the SCOPA-PC is a reliable, valid, and easily-administered semistructured questionnaire for both psychotic and compulsive complications in PD.