Properties of the Apathy Scale (AS) for use on Parkinson’s patients

Parkinson’s disease is a neurodegenerative disorder characterized by motor, autonomic, and neuropsychiatric symptoms, among the latter, apathy has been found to be present in up to 70% of patients. The main objective of the present study was to assess the psychometric properties of the Apathy Scale for evaluation of Ecuadorian patients with Parkinson’s. This was a cross sectional study, with re-test. There were 73 women (34.5%) in the final sample of 211 patients. Mean age was 67.5 ± 10.2 years, mean length of illness was 7.1 ± 5.5 years, and the mean ldopa dose was 656.1 ± 292.7 mg/day. The mean Apathy Scale score was 12.7 ± 7.1. Reliability: The Guttman’s λ obtained was 0.89. The SEM was 2.34 for the AS. The ICC using an absolute agreement definition was: ICC = 0.78 [(95% IC 0.73 - 0.82) f = 4.96; p ≤ 0.000]. Discriminative validity, analyzed with the Kruskal-Wallis statistic and using H&Y stages as segmentation variable registered an X(2) value of p 0.0001. In conclusion the Apathy Scale proved to have suitable metric attributes in this specific PD patient sample: internal consistency, reliability, stability, and convergent and known-groups validity.