Validation of the Portuguese MDS-UPDRS: Challenges to Obtain a Scale Applicable to Different Linguistic Cultures.

Background: The MDS-UPDRS has been available in English since 2008, showing satisfactory clinimetric results and being proposed as the new official benchmark scale for Parkinson's disease (PD), being cited as a core instrument for PD in the National Institutes of Neurological Disorders and Stroke Common Data Elements program. For this reason, the MDS created guidelines for development of MDS-UPDRS official, clinimetrically validated translations.

Objective: This study presents the formal process used to obtain the officially approved Portuguese version of the MDS-UPDRS.

Methods: The study consisted of three phases: (1) Independent translation by Portuguese and Brazilian teams followed by a challenging consensus process that this article particularly emphasizes; (2) Cognitive pretest involving raters and patients from both Portugal and Brazil; (3) Validation test with a sample of 367 native Portuguese-speaking PD patients.

Results: The overall factor structure of the Portuguese version was consistent with the English version based on a comparative fit index ≥0.96 for all four parts of the MDS-UPDRS.

Conclusion: This version can be designated as the official Portuguese version of the MDS-UPDRS.