Psychometric Evaluation of the Impact of Weight on Quality of Life–Lite Clinical Trials (IWQOL-Lite-CT) Version in Adults Participating in a Pharmacological Clinical Trial for Obesity
Author(s)
Ronette L. Kolotkin, PhD1, Andrew G. Bushmakin, M.S.2, Nini Liu-Péré, MSc3, Susan Martin, MSPH4, Joseph C. Cappelleri, PhD2, Joshua T. Swan, PharmD2, Clare Buckeridge, PhD2, Sonia Cobian, MA2, Xuemei Luo, PhD2.
1Quality of Life Consulting, Durham, NC, USA, 2Pfizer Inc., New York City, NY, USA, 3Pfizer Inc., Paris, France, 4RTI Health Solutions, Ann Arbor, MI, USA.
1Quality of Life Consulting, Durham, NC, USA, 2Pfizer Inc., New York City, NY, USA, 3Pfizer Inc., Paris, France, 4RTI Health Solutions, Ann Arbor, MI, USA.
OBJECTIVES: To evaluate the reliability, validity, and ability to detect change of the Impact of Weight on Quality of Life-Lite, Clinical Trials Version (IWQOL-Lite‐CT)—a patient-reported measure assessing weight-related physical and psychosocial functioning in adults with obesity or overweight.
METHODS: This psychometric evaluation used data from trials NCT05579977 (T1) and NCT04707313 (T2). Anchor measures included the 36-item Short Form Health Survey (SF-36) and Patient Global Impression of Severity (PGI-S).
RESULTS: Participants’ (N=1,015) mean ages were 49.1 (T1) and 48.2 (T2) years; mean body mass indexes were 37.8 (NCT05579977) and 38.9 (NCT04707313) kg/m2. For the Physical (PhC), Physical Function (PFC), and Psychosocial (PsC) composites, test-retest reliability (intraclass correlation coefficients >0.70) and internal consistency reliability (Cronbach α >0.70) were acceptable. Differences in composite scores associated with 10-point differences in related SF-36 domains (norm-based scores) supported known-groups validity, with large (standardized) effect sizes for PhC (T1:0.78; T2:0.79) and PFC (0.80;0.78) and small-to-medium effect sizes for PsC (0.50;0.36). Evidence for known-groups validity was also supported, with large effect sizes for PhC (2.10) and PFC (2.18) using PGI-S-based analyses categorizing individuals as “None” or “Very severe” in T1. Evidence for convergent validity was supported via correlations between composites and corresponding SF-36 anchor domains (nearly all Pearson correlation coefficients ≥0.4). Evidence for the ability to detect change was supported by the relationship between changes in the IWQOL-Lite-CT composite and changes in corresponding SF-36 domains. The change in IWQOL-Lite-CT composite associated with 10-point improvements in related SF-36 domains for both trials can be described in terms of effect sizes as medium for the PhC (0.46;0.50) and PFC (0.45;0.49) composites and small-to-medium (0.34;0.24) for the PsC. Floor/ceiling effects were not detected.
CONCLUSIONS: This psychometric evaluation adds evidence to confirm that the IWQOL-Lite-CT is reliable, valid, and able to detect change in evaluations of pharmacological weight loss treatments in clinical trials.
METHODS: This psychometric evaluation used data from trials NCT05579977 (T1) and NCT04707313 (T2). Anchor measures included the 36-item Short Form Health Survey (SF-36) and Patient Global Impression of Severity (PGI-S).
RESULTS: Participants’ (N=1,015) mean ages were 49.1 (T1) and 48.2 (T2) years; mean body mass indexes were 37.8 (NCT05579977) and 38.9 (NCT04707313) kg/m2. For the Physical (PhC), Physical Function (PFC), and Psychosocial (PsC) composites, test-retest reliability (intraclass correlation coefficients >0.70) and internal consistency reliability (Cronbach α >0.70) were acceptable. Differences in composite scores associated with 10-point differences in related SF-36 domains (norm-based scores) supported known-groups validity, with large (standardized) effect sizes for PhC (T1:0.78; T2:0.79) and PFC (0.80;0.78) and small-to-medium effect sizes for PsC (0.50;0.36). Evidence for known-groups validity was also supported, with large effect sizes for PhC (2.10) and PFC (2.18) using PGI-S-based analyses categorizing individuals as “None” or “Very severe” in T1. Evidence for convergent validity was supported via correlations between composites and corresponding SF-36 anchor domains (nearly all Pearson correlation coefficients ≥0.4). Evidence for the ability to detect change was supported by the relationship between changes in the IWQOL-Lite-CT composite and changes in corresponding SF-36 domains. The change in IWQOL-Lite-CT composite associated with 10-point improvements in related SF-36 domains for both trials can be described in terms of effect sizes as medium for the PhC (0.46;0.50) and PFC (0.45;0.49) composites and small-to-medium (0.34;0.24) for the PsC. Floor/ceiling effects were not detected.
CONCLUSIONS: This psychometric evaluation adds evidence to confirm that the IWQOL-Lite-CT is reliable, valid, and able to detect change in evaluations of pharmacological weight loss treatments in clinical trials.
Conference/Value in Health Info
2025-11, ISPOR Europe 2025, Glasgow, Scotland
Value in Health, Volume 28, Issue S2
Code
PCR195
Topic
Patient-Centered Research
Topic Subcategory
Instrument Development, Validation, & Translation
Disease
Diabetes/Endocrine/Metabolic Disorders (including obesity)