Expanded and independent validation of the Movement Disorder Society-Unified Parkinson's Disease Rating Scale (MDS-UPDRS).

The Movement Disorder Society-UPDRS (MDS-UPDRS) was published in 2008, showing satisfactory clinimetric results and has been proposed as the official benchmark scale for Parkinson's disease. The present study, based on the official MDS-UPDRS Spanish version, performed the first independent testing of the scale and adds information on its clinimetric properties. The cross-culturally adapted MDS-UPDRS Spanish version showed a comparative fit index ≥ 0.90 for each part (I-IV) relative to the English-language version and was accepted as the Official MDS-UPDRS Spanish version. Data from this scale, applied with other assessments to Spanish-speaking Parkinson's disease patients in five countries, were analyzed for an independent and complementary clinimetric evaluation. In total, 435 patients were included. Missing data were negligible and moderate floor effect (30 %) was found for Part IV. Cronbach's α index ranged between 0.79 and 0.93 and only five items did not reach the 0.30 threshold value of item-total correlation. Test-retest reliability was adequate with only two sub-scores of the item 3.17, Rest tremor amplitude, reaching κ values lower than 0.60. The intraclass correlation coefficient was higher than 0.85 for the total score of each part. Correlation of the MDS-UPDRS parts with other measures for related constructs was high (≥ 0.60) and the standard error of measurement lower than one-third baseline standard deviation for all subscales. Results confirm those of the original study and add information on scale reliability, construct validity, and precision. The MDS-UPDRS Spanish version shows satisfactory clinimetric characteristics.