Background: Many questionnaires for measuring the quality of life for patients with obesity require comprehensive calculation before they are used. There is a need for questionnaires that permit simple assessment of the responses during a patient consultation. We have developed the questionnaire Patient-Reported Outcomes in Obesity (PROS). The objective of the study was to test the reliability and validity of the questionnaire.
Material and method: The questionnaire was used to ask patients about the extent to which they perceived their weight or body shape as bothersome. A group of patients with an average body mass index (BMI) of 42 (n = 109) completed the PROS questionnaire and The Impact of Weight Quality of Life questionnaire (IWQOL-Lite) before undergoing obesity surgery. Another group with an average body mass index of 29 (n = 95) completed the PROS questionnaire 1-5 years after having undergone obesity surgery. 67,7 % of the patients were > 40 years and 79 % were women. For the statistical analysis we used Cronbach's alpha, factor analysis, Spearman's rank test and independent t-test.
Results: Cronbach's alpha for the total PROS score was 0.90, and the factor analysis showed a significant factor (eigenvalue = 4.7) that explained 58.4 % of the variance. The test-retest correlation was 0.93 (p < 0.001). The correlation coefficients between the PROS score, the total IWQOL-Lite score (rs = -0.91) and body mass index (rs = 0.60) were all significant (p < 0.001). The t-test showed an effect size (difference in standard deviation) between the non-surgery and the surgery groups of 1.9 (95 % CI 1.6-2.5) for the PROS questionnaire and 2.1 (95 % CI 1.7-2.5 for the total IWQOL-Lite score.
Interpretation: The PROS questionnaire is a reliable and valid questionnaire for measurement of obesity-specific quality of life.