Reliability and validity of the brief dimensional apathy scale

Objective: Apathy is composed of different demotivational subtypes measurable by the dimensional apathy scale (DAS) and can be quickly assessed using the brief DAS (b-DAS). The aim was to determine the reliability and validity of the b-DAS. Methods: 53 amyotrophic lateral sclerosis (ALS) patients and 53 of their informants were recruited. Informants completed the b-DAS, the original informant/carer-rated DAS and behavioral interview about the patients (i.e., presence of behaviors such as apathy/inertia, loss of sympathy/empathy). Patients completed measures of depression, anxiety, emotional lability, cognitive functioning, and functional disability measures. Results: The b-DAS showed good internal consistency, excellent test-retest reliability, significant positive correlation with the original DAS, and no significant correlations with depression, anxiety, emotional lability, cognitive functioning or functional disability measures. Semi-structured behavior interview showed patients with apathy/inertia had significantly higher b-DAS subscale scores and patients with loss of sympathy/empathy had significantly higher emotional apathy scores only. Conclusions: The b-DAS is a fast, reliable, and valid instrument for screening apathy subtypes independent of physical disability.