Assessing apathy in multiple sclerosis: Validation of the dimensional apathy scale and comparison with apathy evaluation scale

Background: Apathy is a predictor of cognitive decline in the course of multiple sclerosis (MS). Early identification of apathetic patients is relevant in clinical settings. Objective: To assess applicability and psychometric properties of the self-rated version of the Dimensional Apathy Scale (DAS) in a large cohort of patients with MS and to compare its diagnosing accuracy with that of the Apathy Evaluation Scale (AES). Methods: One hundred and twenty-four patients underwent clinical interview based on diagnostic criteria for apathy, DAS, AES, and assessment of depression, global cognitive functioning, and non-verbal intelligence. Results: According to diagnostic criteria, apathy occurred in 33.4% of the patients. The DAS showed high consistency, and good convergent, discriminant and criterion validity. Factor analysis indicated a three-factor structure: executive, behavioural and emotional apathy. Unlike AES, no significant association between DAS score and severity of neurological disability (expressed by EDSS total score) was found, suggesting that the DAS might be less related to levels of disability. Receiver operating characteristics analyses, with clinical diagnostic criteria for apathy as the gold standard, revealed that a DAS score of 28/29 and an AES score of 35/36 were optimal cut-off values for identifying clinically relevant apathy. The two scales had similar diagnostic accuracy in the present sample. Conclusions: The DAS is a valid and reliable multidimensional tool to assess apathy in MS, with diagnostic accuracy similar to that of the AES. However, the DAS score appears to be less strongly related to neurological disability.