title: Psychometric properties of the General Self-Efficacy Scale in Parkinson's disease.
abstract: OBJECTIVE
  This study aimed to investigate the psychometric properties of the General Self-Efficacy Scale (GSE) in people with Parkinson's disease (PD). More specifically, we investigated data completeness, scaling assumptions, targeting, reliability, and construct validity.
  
  
  METHODS
  This study involves data available from two different projects that included people diagnosed with PD for at least 1 year, yielding two samples (1 and 2). The combined total sample (N=346; 60% men) had a mean (SD) age and PD duration of 71 (8.9) and 9 years (6.3), respectively. Both samples received a self-administered survey by mail, which was administered twice in sample 2. Additional data (e.g., clinical assessments) were available for Sample 1.
  
  
  RESULTS
  Total GSE scores were computable for 336 participants (97%). Corrected item-total correlations exceeded 0.4. Principal component analyses identified one component (the eigenvalue of the first component extracted was 6.9), explaining 69% of the total variance. Floor and ceiling effects were <6%. Internal consistency (coefficient alpha) was 0.95. Analyses of test-retest reliability yielded (ICC) values from 0.69 to 0.80. The highest value refers to those (n=47) with identical self-ratings of mobility (in the on condition) at both tests; the standard error of measurement was 3.1 points. Construct validity was further supported by correlations in accordance with a priori expectations.
  
  
  CONCLUSIONS
  This study provides support for the validity and reliability of GSE scores in people with PD; the GSE can thus serve as a valuable outcome measurement in clinical practice and research.
authors: Department of Health Sciences, Lund University, Lund, Sweden.
authors: M H
authors: MH
authors: Nilsson
authors: The PRO-CARE Group, School of Health and Society, Kristianstad University, Kristianstad, Sweden.
authors: P
authors: P
authors: Hagell
authors: Department of Health Sciences, Lund University, Lund, Sweden.
authors: S
authors: S
authors: Iwarsson
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000175:diagnosis / Q000523:psychology*; D011594:Psychometrics / Q000379:methods*; D015203:Reproducibility of Results; D011795:Surveys and Questionnaires
keywords: Parkinson's disease; patient outcome assessment; psychometrics; questionnaires; rehabilitation; reliability and validity; self-efficacy