Simplified conversion method for unified Parkinson's disease rating scale motor examinations

Background: We evaluated a simplified method for converting Unified Parkinson's Disease Rating Scale Part III Motor Examination total scores (UPDRS III) to the International Parkinson and Movement Disorder Society's (MDS) revised version of the scores. Methods: PD patients in the Arizona Study of Aging and Neurodegenerative Disorders were assessed with both scales. The accuracy of the predicted scores was assessed using regression modeling, classical intraclass correlation coefficients, and the Bland-Altman method. Results: There was strong correlation between the two scores. Adding 7 points to a UPDRS III total score performed approximately as well as previously published conversion formulas (intraclass correlation: 0.96). The adjusted score is expected to be within 3 points of the MDS-UPDRS III score 50% of the time and within 9 points 95% of the time. Conclusions: Simply adding 7 points to a UPDRS III total score provides a good approximation of the MDS-UPDRS III total score.