The General Self-Efficacy Scale in a population planned for bariatric surgery in Sweden: a psychometric evaluation study

OBJECTIVES: This study psychometrically evaluated General Self-Efficacy (GSE) Scale in patients planned for bariatric surgery in Sweden. DESIGN: A cross-sectional psychometric study. The psychometric evaluation was guided by the COnsensus-based Standards for the selection of health status Measurement Instruments checklist for health-related reported-patient outcomes. SETTING: Three bariatric centres in Sweden. PARTICIPANTS: Adult patients≥18 years old scheduled for primary bariatric surgery (with sleeve gastrectomy or Roux-en-Y gastric bypass). PRIMARY AND SECONDARY MEASURES: Psychometric properties of the GSE. RESULTS: In total, 704 patients were included in the analysis. Mean values for GSE items were 2.9–3.4 and the mean GSE sum score was 31.4 (SD 4.7). There were no floor or ceiling effects. Cronbach’s alpha was 0.89. Men reported a higher mean GSE than did women, that is, 31.2 (SD 4.8) for women versus 32.1 (SD 4.3) for men, p=0.03. Correlation coefficients were weak or negligible: GSE and mental component summary score of 36-Item Short Form Health Survey (SF-36)/RAND 36, r=0.18 (p<0.00); GSE and physical component summary score of SF-36/RAND 36, r=0.07 (p=0.138); GSE and obesity-related problem scale r=−0.15 (p=0.001) and GSE and level of education, r=0.04 (p=0.35). Confirmatory factor analysis indicated a one-factor construct with a satisfactory goodness of fit, that is, Comparative Fit Index=0.927, root mean square error of approximation=0.092 and standardised root mean square residual=0.045. The factor GSE explained almost half or over half of the variance of each item (0.45–0.75, p-values<0.001). CONCLUSIONS: The GSE scale is a valid and reliable scale that can be used to assess general self-efficacy in patients undergoing bariatric surgery.