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OBJECTIVE	Optimizing assessments of rate of progression in Parkinson disease ( PD ) is important in designing clinical trials , especially of potential disease-modifying agents .
OBJECTIVE	To examine the value of measures of impairment , disability , and quality of life in assessing progression in early PD .
METHODS	Inception cohort analysis of data from 413 patients with early , untreated PD who were enrolled in 2 multicenter , randomized , double-blind clinical trials .
METHODS	Participants were randomly assigned to 1 of 5 treatments ( 67 received creatine , 66 received minocycline , 71 received coenzyme Q10 , 71 received GPI-1485 , and 138 received placebo ) .
METHODS	We assessed the association between the rates of change in measures of impairment , disability , and quality of life and time to initiation of symptomatic treatment .
METHODS	Time between baseline assessment and need for the initiation of symptomatic pharmaceutical treatment for PD was the primary indicator of disease progression .
RESULTS	After adjusting for baseline confounding variables with regard to the Unified Parkinson 's Disease Rating Scale ( UPDRS ) Part II score , the UPDRS Part III score , the modified Rankin Scale score , level of education , and treatment group , we assessed the rate of change for the following measurements : the UPDRS Part II score ; the UPDRS Part III score ; the Schwab and England Independence Scale score ( which measures activities of daily living ) ; the Total Functional Capacity scale ; the 39-item Parkinson 's Disease Questionnaire , summary index , and activities of daily living subscale ; and version 2 of the 12-item Short Form Health Survey Physical Summary and Mental Summary .
RESULTS	Variables reaching the statistical threshold in univariate analysis were entered into a multivariable Cox proportional hazards model using time to symptomatic treatment as the dependent variable .
RESULTS	More rapid change ( ie , worsening ) in the UPDRS Part II score ( hazard ratio , 1.15 [ 95 % CI , 1.08-1 .22 ] for 1 scale unit change per 6 months ) , the UPDRS Part III score ( hazard ratio , 1.09 [ 95 % CI , 1.06-1 .13 ] for 1 scale unit change per 6 months ) , and the Schwab and England Independence Scale score ( hazard ratio , 1.29 [ 95 % CI , 1.12-1 .48 ] for 5 percentage point change per 6 months ) was associated with earlier need for symptomatic therapy .
CONCLUSIONS	AND RELEVANCE In early PD , the UPDRS Part II score and Part III score and the Schwab and England Independence Scale score can be used to measure disease progression , whereas the 39-item Parkinson 's Disease Questionnaire and summary index , Total Functional Capacity scale , and the 12-item Short Form Health Survey Physical Summary and Mental Summary are not sensitive to change .
BACKGROUND	clinicaltrials.gov Identifiers : NCT00063193 and NCT00076492 .

