Reliability and validity of the brief Dimensional Apathy Scale (b-DAS)

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. Method: 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 behavioural interview about the patients (i.e. presence of behaviours 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 behaviour 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.