Implementation of the IWQOL-Lite-CT in Observational Research: Comparison of Baseline Scores With a Clinical Trial Population and Psychometric Evaluation.

The aims of this study were to compare baseline Impact of Weight on Quality of Life-Lite Clinical Trials Version (IWQOL-Lite-CT) scores between adults with obesity participating in either observational or clinical studies and to conduct a psychometric evaluation of the IWQOL-Lite-CT in the context of observational research. Analyses of covariance were used to compare baseline IWQOL-Lite-CT Total, Physical, Physical Function, and Psychosocial composite scores between participants with a body mass index (BMI) ≥ 30 in a US longitudinal survey (an observational study) and a multinational phase 3a study of subcutaneous semaglutide 2.4 mg for weight management (STEP 1). Data from the longitudinal survey were also used to evaluate the psychometric properties of the IWQOL-Lite-CT composite scores. Adjusting for BMI, age, and sex, on average, participants in the longitudinal survey scored lower than STEP 1 participants at baseline by 23.4 points on the IWQOL-Lite-CT Total, 20.7 on the Physical composite, 20.3 on the Physical Function composite, and 24.8 on the Psychosocial composite. While the internal consistency, test-retest reliability, and construct validity of the IWQOL-Lite-CT composite scores were confirmed in the longitudinal survey, responsiveness analyses were limited by small changes in weight. The weight-related functioning of US individuals with obesity who participated in a longitudinal survey was more limited than that of participants in the STEP 1 clinical trial. Psychometric results support use of the IWQOL-Lite-CT in observational research in addition to the clinical trial setting.