Confirmatory psychometric evaluations of the Impact of Weight on Quality of Life–Lite Clinical Trials Version (IWQOL-Lite-CT)

Abstract

The Impact of Weight on Quality of Life–Lite Clinical Trials Version (IWQOL-Lite-CT) was developed to assess weight-related physical and psychosocial functioning in the context of clinical trials. Data from two pivotal trials of once-weekly subcutaneous semaglutide for the purpose of weight management (NCT03548935 and NCT03552757) were analysed to confirm the structure, reliability, validity, and responsiveness of the IWQOL-Lite-CT and evaluate the magnitude of meaningful within-patient change in patients with overweight or obesity, with and without type 2 diabetes. Factor analyses and inter-item correlations confirmed the IWQOL-Lite-CT structure and scoring algorithm. Each composite score (physical, physical function, psychosocial, and total) demonstrated excellent internal consistency (Cronbach's alphas ≥ 0.82) and test–retest reliability (intraclass correlation coefficients ≥ 0.85) in both trials. Patterns of cross-sectional and longitudinal construct validity correlations were generally consistent with hypotheses. Each of the IWQOL-Lite-CT composites was able to discriminate between known groups. Effect sizes and paired t tests comparing IWQOL-Lite-CT scores at baseline and Week 68 were statistically significant for all composites in both trials (P < 0.0001), providing strong support for the ability to detect change. Results of anchor-based analyses supported responder thresholds ranging from 13.5 to 16.6 across composite scores. The IWQOL-Lite-CT, a comprehensive assessment of weight-related functioning from the patient perspective, is appropriate for use in clinical trials evaluating the efficacy of new treatments for weight management.