A short Scale for Evaluation of Neuropsychiatric Disorders in Parkinson’s Disease: first psychometric approach

The neuropsychiatric symptoms and behavioral disorders affecting Parkinson’s disease (PD) patients are common and disabling. A PD-specific interview-based 12-item scale, the Scale for Evaluation of Neuropsychiatric Disorders in Parkinson’s Disease (SEND-PD), has been developed to assess the severity of neuropsychiatric manifestations. The present study is aimed at testing some basic psychometric attributes of this scale. A total of 633  consecutive patients and their caregivers were included in this cross-sectional, multicenter, observational study. In addition to the tested scale, the following assessments were applied: Hoehn and Yahr staging, Scales for Outcomes in Parkinson’s Disease Motor and Psychiatric complications, MiniMental State Examination, Clinical Impression of Severity Index, and the Zarit Caregiver Burden Inventory. Patients in all stages of disease were included and 18.38 % were demented. The SEND-PD was responded by patients (86.16 %), caregivers (13.15 %), or both (0.69 %). Three factors (accounting for 66.63 % of the variance) were identified and considered as subscales: Psychotic symptoms, Mood/Apathy, and Impulse control disorders. The subscales showed satisfactory scaling assumptions (multitrait-item success rate 100 %) and internal consistency (alpha indices >0.70). The convergent validity with other measures of psychiatric symptoms and the discriminant validity to distinguish between categories of patients’ age, duration and severity of disease, and dopaminergic treatment were satisfactory. The precision of the scale dimensions was acceptable. The SEND-PD performed as an acceptable, consistent, valid, and precise scale for evaluation of neuropsychiatric symptoms in Parkinson’s disease.