title: Psychometric validation of the revised SCOPA-Diary Card: expanding the measurement of non-motor symptoms in Parkinson's disease.
abstract: BACKGROUND
  To identify key non-motor symptoms of Parkinson's disease (PD) to include in a daily diary assessment for off-time, revise the Scales for Outcomes of Parkinson's disease Diary Card (SCOPA-DC) to include these non-motor symptoms, and investigate the validity, reliability and predictive utility of the Revised SCOPA-DC in a U.S. population.
  
  
  METHODS
  A convenience sample was used to recruit four focus groups of PD patients. Based on findings from focus groups, the SCOPA-DC was revised and administered to a sample of 101 PD patients. Confirmatory factor analysis was conducted to test the domain structure of the Revised SCOPA-DC. The reliability, convergent and discriminant validity, and ability to predict off-time of the Revised SCOPA-DC were then assessed.
  
  
  RESULTS
  Based on input from PD patients, the Revised SCOPA-DC included several format changes and the addition of non-motor symptoms. The Revised SCOPA-DC was best represented by a three-factor structure: Mobility, Physical Functioning and Psychological Functioning. Correlations between the Revised SCOPA-DC and other Health-Related Quality of Life scores were supportive of convergent validity. Known-groups validity analyses indicated that scores on the Revised SCOPA-DC were lower among patients who reported experiencing off-time when compared to those without off-time. The three subscales had satisfactory predictive utility, correctly predicting off-time slightly over two-thirds of the time.
  
  
  CONCLUSIONS
  These findings provide evidence of content validity of the Revised SCOPA-DC and suggest that a three-factor structure is an appropriate model that provides reliable and valid scores to assess symptom severity among PD patients with symptom fluctuations in the U.S.
authors.affiliation: QualityMetric Inc, Lincoln, RI, USA.
authors.forename: Regina
authors.initials: R
authors.lastname: Rendas-Baum
authors.forename: Philip O
authors.initials: PO
authors.lastname: Buck
authors.forename: Michelle K
authors.initials: MK
authors.lastname: White
authors.forename: Jane
authors.initials: J
authors.lastname: Castelli-Haley
mesh_terms: D003430:Cross-Sectional Studies; D015259:Dopamine Agents / Q000008:administration & dosage* / Q000493:pharmacokinetics / Q000627:therapeutic use; D005163:Factor Analysis, Statistical; D017144:Focus Groups; D006801:Humans; D016015:Logistic Models; D008499:Medical Records / Q000592:standards*; D010300:Parkinson Disease / Q000188:drug therapy* / Q000503:physiopathology*; D011594:Psychometrics; D015203:Reproducibility of Results; D018709:Statistics, Nonparametric; D013997:Time Factors; D014481:United States
chemical_list: D015259:Dopamine Agents