Background: Individuals experiencing apathy in Parkinson's disease (PD) have a lack of emotion and motivation. Apathy often overlaps with comorbidities such as depression, and is sometimes difficult to detect.
Objective: To examine diagnostic accuracy of apathy-screening tools compared with a gold standard (clinician diagnosis) among adult outpatients with PD.
Methods: A systematic review was conducted. Six research databases were searched to May 23, 2018. Diagnostic accuracy measures, including sensitivity and specificity were gathered.
Results: 1,007 full-text articles were reviewed with seven full-text articles included. The gold standard was considered a clinician diagnosis as apathy is not defined in the DSM/ICD. Diagnostic accuracy measures were reported for the Lille Apathy Rating Scale (LARS) both informant- and observer-rated, Unified Parkinson's Disease Rating Scale (UPDRS), Apathy Scale (AS), Apathy Evaluation Scale (AES), Non-Motor Symptoms Questionnaire (NMS-Q), and Dimensional Apathy Scale (DAS). The AES had the best reported sensitivity and specificity values, both 90%. The AS had the highest reported specificity at 100%, with 66% sensitivity. Pooled prevalence of apathy was 29.1% (95% CI 21.5%-36.6%).
Conclusions: While 18 screening tools exist to screen for apathy in PD, only six have been validated against clinician diagnosis. The AES had the highest reported sensitivity and specificity and is a brief, easy to use tool. The AS was designed specifically for use in PD populations and has the highest reported specificity. Future research should focus on the development of an accepted gold standard, to further understand accuracy measures of all available apathy screening tools.
Keywords: Parkinson’s disease; apathy; diagnosis; diagnostic tools.