Apathy is reported in 16.5% to 70% of Parkinson's disease (PD) patients. Our recently developed Lille Apathy Rating Scale (LARS) has been specifically validated for patient-based assessment of apathy in PD. The aim of the present study was to validate a caregiver-based version of the LARS. Sixty consecutive PD patients and their respective caregivers participated in the study. An informant-based version of the LARS (LARS-i) was developed to rate apathy via a caregiver-based structured interview. Apathy was also assessed in a patient-based interview using the LARS and the informant- and clinician-rated versions of the Apathy Evaluation Scale (AES). Cronbach's alpha and standardized alpha coefficients were 0.872 and 0.877, respectively, and the split-half reliability was 0.901 (revealing good internal consistency). The test-retest and inter-rater reliability values were 0.960 and 0.996, respectively. Criterion-related validity (according to an independent, expert diagnosis) was good. Scores on the LARS and the LARS-i were highly correlated. However, apathy was rated significantly more severely by the caregiver than by the patient. This difference was significantly higher for demented than nondemented PD patients. The LARS-i was seen to have excellent psychometric properties and appears to be valid for use in PD with respect to the patient-based LARS and the informant- and clinician-rated versions of the AES.
(c) 2008 Movement Disorder Society.