Patient-reported quality of life with obesity - development of a new measurement scale

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.

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.

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.

The PROS questionnaire is a reliable and valid questionnaire for measurement of obesity-specific quality of life.