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.