Inter-rater reliability of hand motor function assessment in Parkinson's disease: Impact of clinician training

Medication adjustments in Parkinson's disease (PD) are driven by patient subjective report and clinicians' rating of motor feature severity (such as bradykinesia and tremor). Objective: As patients may be seen by different clinicians at different visits, this study aims to determine the interrater reliability of upper limb motor function assessment among clinicians treating people with PD (PwPD). Methods: PwPD performed six standardised hand movements from the Movement Disorder Society's Unified Parkinson's Disease Rating Scale (MDS-UPDRS), while two cameras simultaneously recorded. Eight clinicians independently rated tremor and bradykinesia severity using a visual analogue scale. We compared intraclass correlation coefficient (ICC) before and after a training/calibration session where high-variance participant videos were reviewed and MDS-UPDRS instructions discussed. Results: In the first round, poor agreement was observed for most hand movements, with best agreement for resting tremor (ICC 0.66 bilaterally; right hand 95 % CI 0.50-0.82; left hand: 0.50-0.81). Postural tremor (left hand) had poor agreement (ICC 0.14; 95% CI 0.04-0.33), as did wrist pronation-supination (right hand ICC 0.34; 95 % CI 0.19-0.56). In post-training rating exercises, agreements improved, especially for the right hand. Best agreement was observed for hand open-close ratings in the left hand (ICC 0.82, 95 % CI 0.64-0.94) and resting tremor in the right hand (ICC 0.92, 95 % CI 0.83-0.98). Discrimination between right and left hand features by raters also improved, except in resting tremor (disimprovement) and wrist pronation-supination (no change). Conclusions: Clinicians vary in rating video-recorded PD upper limb motor features, especially bradykinesia, but this can be improved somewhat with training.