The prototype of a preference-based index of weight-related quality of life: demonstrating the possibilities.

PURPOSE: Evidence for comparative and cost-effectiveness of weight-loss interventions is lacking as there are no obesity-specific measures fit for this purpose. This study aimed to estimate the extent to which a prototype of a brief, multi-dimensional obesity-specific Preference-Based Index of Weight-Related Quality of Life (PBI-WRQL) could fill this gap. METHODS: Longitudinal data from a Canadian bariatric cohort was used. Forty-eight items from the IWQoL-Lite, EQ-5D-3L, and SF-12V2 were mapped onto the WHO ICF domains, and one item was chosen for the dimension based on fit to the Rasch model. Individuals' health ratings (0-100) were regressed on each dimension, and the regression coefficients for the response options were used as weights to generate a total score. Generalized estimation equations were used to compare measure parameters across groups and levels of converging constructs. RESULTS: Pre-surgery data were available on 201 people (Women: 82%; BMI: 48.8 ± 6.7 kg/m2; age: 43 ± 9.0 years) and on 125 (62%) at 6 months post-bariatric surgery. Seven dimensions with three response options formed the PB-WRQL prototype: Mobility/Physical Function, Pain, Depression, Participation, Energy, Peripheral Edema, and Dyspnea. The prototype showed substantial change (mean + 40) with bariatric surgery, higher than the EQ-5D (mean + 11.5). The prototype showed the strongest relationship with BMI at baseline (t = - 3.68) and was the most sensitive to change in BMI (t = - 3.42). CONCLUSION: This study demonstrates that a brief, 7-dimension index weighted by health impact performed as well as the 31-item IWQoL-Lite and better than the EQ-5D-3L. These findings demonstrate the potential value of the brief PB-WRQL prototype index and support its further development using preference weights to reflect the current generation's needs and concerns.