Treatment effect modifiers for the patient education programme for Parkinson’s disease

Summary Aim:  A recent randomised controlled trial showed significant benefits for Parkinson’s disease (PD) caregivers’ psychosocial problems and need for help and a trend towards significant improvement of patients’ quality of life after participation in the Patient Education Programme for Parkinson’s disease (PEPP). Large variations in change scores were found, indicating variation in benefit. The aim of this study was to search for treatment effect modifiers. Methods:  Outcome measures were patients’ quality of life [Parkinson’s Disease Questionnaire (PDQ)-39] and caregivers’ psychosocial burden [Belastungsfragebogen Parkinson Angehorigen kurzversion (BELA-A-k)]. Candidate treatment effect modifiers were participants’ characteristics and baseline scores on psychological questionnaires (BELA-P/A-k, PDQ-39, EQ-5D, Self-rating Depression Scale) and patients’ neuropsychological test scores (Mini Mental State Examination, National Adult Reading Test, Dutch version, Word Test, Behavioural Assessment of the Dysexecutive Syndrome rule shift, Trail Making Test, Stroop). Secondary analyses of data from a randomised controlled trial with 64 patients and 46 caregivers were performed using regression analyses with treatment group interaction terms. Results:  No significant modifiers were found for the patients. In the caregiver group, a higher MMSE score of the patient at baseline was found to be a significant predictor of a lower BELA-A-k Bothered by score post-intervention of the caregiver. Conclusions:  A potential predictor of treatment benefit was found for caregivers of PD patients with better cognitive functioning. This study did not find treatment effect modifiers for PD patients: demographics, disease stage and time of diagnosis, cognitive functioning, level of baseline psychosocial burden, participating with or without a caregiver, and caregiver changes did not influence treatment outcome. The PEPP seems suitable for the majority of patients.