Validation of diagnostic criteria for apathy in Parkinson's disease

Background: Apathy is a common neuropsychiatric syndrome in Parkinson's Disease (PD) that affects quality of life. Research into apathy has been hampered by a lack of broadly accepted diagnostic criteria. Recently, diagnostic criteria for apathy in neuropsychiatric disorders have been proposed, which to date have not been validated in PD. Aim: To validate the proposed diagnostic criteria for apathy in PD. Design and methods: In a cross-sectional study, outpatients with PD visiting a movement disorders clinic underwent a protocolized assessment of motor function, activities of daily living (ADL), cognition and mood. In addition, the diagnostic criteria for apathy were administered as well as two apathy rating instruments: the Lille Apathy Rating Scale (LARS) and the apathy section of the Neuropsychiatric Inventory (NPI). Results: Of the included patients 17.2% were diagnosed with apathy according to the criteria. Acceptability and internal consistency of the criteria was good, as was the concurrent validity with the LARS and apathy section of the NPI. Discriminant validity of the criteria with depression was moderate to good. All domains of criterion B (behavior, cognition, emotion) contributed to the diagnosis of apathy, of which reduced goal-directed behavior was the most frequently observed symptom. Conclusion: The recently proposed diagnostic criteria for apathy are useful in clinical practice and in research with PD patients with and without cognitive impairment