Validation of a new measure of quality of life in obesity trials: Impact of Weight on Quality of Life-Lite Clinical Trials Version

Abstract

The Impact of Weight on Quality of Life-Lite (IWQOL-Lite) is widely used in evaluations of weight-loss interventions, including pharmaceutical trials. Because this measure was developed using input from individuals undergoing intensive residential treatment, the IWQOL-Lite may include concepts not relevant to clinical trial populations and may be missing concepts that are relevant to these populations. An alternative version, the IWQOL-Lite Clinical Trials Version (IWQOL-Lite-CT), was developed and validated according to the US Food and Drug Administration's (FDA's) guidance on patient-reported outcomes. Psychometric analyses were conducted to validate the IWQOL-Lite-CT using data from two randomized trials (NCT02453711 and NCT02906930) that included individuals with overweight/obesity, with and without type 2 diabetes. Additional measures included the SF-36, global items, weight and body mass index. The IWQOL-Lite-CT is a 20-item measure with two primary domains (Physical [seven items] and Psychosocial [13 items]). A five-item Physical Function composite and Total score were also supported. Cronbach's alpha and intraclass correlation coefficients exceeded 0.77 at each time point; patterns of construct validity correlations were consistent with hypotheses; and scores demonstrated treatment benefit. The IWQOL-Lite-CT is appropriate for assessing weight-related physical and psychosocial functioning in populations commonly targeted for obesity clinical trials. Qualification from the FDA is being sought for use of the IWQOL-Lite-CT in clinical trials to support product approval and labelling claims.

Keywords: Impact of Weight on Quality of Life-Lite (IWQOL-Lite); Impact of Weight on Quality of Life-Lite Clinical Trials Version (IWQOL-Lite-CT); health-related quality of life; patient functioning; psychometric validation.