• 1
    Goetz CG, Fahn S, Martinez-Martin P, et al. Movement Disorder Society-sponsored revision of the Unified Parkinson's Disease Rating Scale (MDS-UPDRS): process, format, and clinimetric testing plan. Mov Disord 2007;22:4147.
  • 2
    Goetz CG, Tilley BC, Shaftman SR, et al. Movement Disorder Society-sponsored revision of the Unified Parkinson's Disease Rating Scale (MDS-UPDRS): scale presentation and clinimetric testing results. Mov Disord 2008;23:21292170.
  • 3
    Goetz CG, Nutt JG, Stebbins GT. The Unified Dyskinesia Rating Scale: presentation and clinimetric profile. Mov Disord 2008;23:23982403.
  • 4
    Tilley BC, La Pelle NR, Goetz CG, Stebbins GT. Using cognitive pretesting in scale development for Parkinson's disease: the Movement Disorder Society Unified Parkinson's Disease Rating Scale (MDS-UPDRS) Example. J Parkinsons Dis 2014. [Epub ahead of print] PMID: 24613868.
  • 5
    Gorsuch RL. Factor Analysis. 2nd ed. Hillsdale, NJ: Lawrence Erlbaum Associations Inc; 1983.
  • 6
    Hatcher L. Step-by-Step Approach to Using the SAS System for Factor Analysis and Structural Equation Modeling. Cary, NC: SAS Institute; 1994.
  • 7
    Muthen LK, Muthen BO. Mplus User's Guide. 6th ed. Los Angeles, CA: Muthen & Muthen; 2010.
  • 8
    Brown TA. Confirmatory Factor Analysis for Applied Research. New York, NY: Guilford Sage Publications Inc; 2006.
  • 9
    Forero CG, Maydeu-Olivares A, Gallardo-Pujol D. Factor analysis with ordinal indicators: a Monte Carlo study comparing DWLS and ULS estimation. Struct Equ Model 2009;16:625641.
  • 10
    Browne MW. An overview of analytic rotation in exploratory factor analysis. Multivar Behav Res 2001;36:111150.
  • 11
    Movement Disorder Society Task Force on Rating Scales for Parkinson's Disease. The Unified Parkinson's Disease Rating Scale (UPDRS): status and recommendations. Mov Disord 2003;18:738750.
  • 12
    Colosimo C, Martinez-Martin P, Fabbrini G, et al. Task force report on scales to assess dyskinesia in Parkinson's disease: critique and recommendations. Mov Disord 2010;25:11311142.
  • 13
    Lewitt PA, Hauser RA, Lu M, et al. Randomized clinical trial of fipamezole for dyskinesia in Parkinson disease (FJORD study). Neurology 2012;79:163169.
  • 14
    Rodriguez-Blazquez C, Rojo-Abuin JM, Alvarez-Sanchez M, et al. The MDS-UPDRS Part II (motor experiences of daily living) resulted useful for assessment of disability in Parkinson's disease. Parkinsonism Relat Disord 2013;19:889893.