Background: Health-related quality of life and patient functioning are important secondary outcomes in clinical trials. The Impact of Weight on Quality of Life–Lite (IWQOL-Lite) is widely used in evaluations of diverse weight-loss interventions, including pharmaceutical trials. Developed prior to the Food and Drug Administration’s (FDA) guidance on the use of patient-reported outcome measures, the IWQOL-Lite lacks the developmental rigor required to support product labeling. An alternative version was developed and validated in accordance with the guidance: IWQOL-Lite Clinical Trials Version (IWQOL-CT).
Methods: Based on input from clinical experts, FDA, and concept elicitation interviews, a pool of items selected and/or modified from the IWQOL-Lite or developed de novo was assembled. Subsequent refinement through cognitive debriefing interviews resulted in a 23-item pilot measure. Interviews with 42 individuals with obesity and 29 with type 2 diabetes and body mass index (BMI) ≥27 supported development of the IWQOL-CT. Psychometric analyses were conducted using IWQOL-CT data from two randomized trials, plus SF-36 scores, global items, and BMI at baseline and follow-up visits.
Results: After eliminating items with high inter-item correlations or poor responsiveness, a 20-item measure with two primary domains [physical (7 items) and psychosocial (13 items)] remained. Psychometric analyses supported reliability, validity, and responsiveness of the IWQOL-CT physical and psychosocial domains, and a physical function composite score. Cronbach’s alpha and intraclass correlation coefficients exceeded 0.80 for all three scores at each time point, and patterns of construct validity correlations were consistent with expectations.
Conclusions: The IWQOL-CT is a reliable, valid, and responsive measure of weight-related functioning in the populations commonly targeted for clinical trials of new weight-loss medications. We anticipate qualification by FDA of the IWQOL-CT for this context of use to support product labeling.
