title: Psychometric properties of the Perceived Therapeutic Efficacy Scale for adhering to a cholesterol-lowering diet.
abstract: BACKGROUND
  Outcome expectancy may play an important role in behavior change. Previous studies tested the validity and the reliability of the Perceived Therapeutic Efficacy Scale (PTES), a scale that measures outcome expectancy related to adhering to a cholesterol-lowering diet. Further study was needed to examine its psychometric properties in a larger sample.
  
  
  OBJECTIVE
  The aim of this study was to test the psychometric properties of the 10-item PTES in a large sample.
  
  
  METHODS
  The PTES and the Connor Diet Habit Survey were administered to adults enrolled in a cardiac rehabilitation program.
  
  
  RESULTS
  The final sample for the analysis (N = 224) was, on average, 69.35 years old and was predominantly men (66.50%) and white (92.40%); nearly all (96.00%) completed high school. The inter-item correlation matrix revealed that correlation coefficients were greater than 0.80 between 4 pairs of items, suggesting that the 4 items were redundant. After consulting with a content expert and an examination of item content, we removed the 4 redundant items (items 2, 3, 4, and 10) and reduced the scale to 6 items. Principal component analysis revealed a 1-factor scale with high loadings for the 6 items, each greater than 0.70. The reliability of the scale, measured by Cronbach's α, was 0.91. The total PTES score had a moderate correlation with self-reported behaviors of adhering to a cholesterol-lowering diet, as measured by the Connor Diet Habit Survey subscale for cholesterol and fat intake (r = 0.36, P < 0.05).
  
  
  CONCLUSIONS
  This study demonstrated that the revised and shortened PTES scale is reliable and valid to measure outcome expectancy related to adhering to a cholesterol-lowering diet.
authors.affiliation: Yaguang Zheng, MSN PhD student, Department of Health and Community Systems, School of Nursing, University of Pittsburgh, Pennsylvania. Lauren Terhorst, MA, PhD Clinical Outcomes Analyst, University of Pittsburgh Medical Center, Pennsylvania. Jina Choo, PhD, DrPH, RN Associate Professor of Community Health Nursing, College of Nursing, Korea University, Seoul, South Korea. Lora E. Burke, PhD, MPH Professor of Nursing, Epidemiology and Clinical and Translational Science Institute, University of Pittsburgh, Pennsylvania.
authors.forename: Yaguang
authors.initials: Y
authors.lastname: Zheng
authors.forename: Lauren
authors.initials: L
authors.lastname: Terhorst
authors.forename: Jina
authors.initials: J
authors.lastname: Choo
authors.forename: Lora E
authors.initials: LE
authors.lastname: Burke
mesh_terms: D000368:Aged; D003430:Cross-Sectional Studies; D018752:Diet, Fat-Restricted; D005163:Factor Analysis, Statistical; D005260:Female; D006801:Humans; D008297:Male; D025341:Principal Component Analysis; D011594:Psychometrics; D020377:Self Efficacy