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

Abstract

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.