Background: Obesity is a chronic disease with significant impacts on health-related quality of life (HRQoL) specifically physical functioning (PF), which is increasingly assessed using PRO measures in clinical trials. A review of existing literature suggested that further qualitative research was required to establish patient-perceived clinically important change (CIC) thresholds for two PRO measures used in obesity studies: the acute 36-item Short Form Health Survey (SF-36v2) and Impact of Weight on Quality of Life-Lite-Clinical Trials Version (IWQOL-Lite-CT).

Objective: To explore the level of change on the SF-36v2 (acute) and IWQOL-Lite-CT that individuals living with obesity consider to be meaningful, noticeable and indicative of treatment success.

Methods: Semi-structured interviews were conducted in the U.S. with adults who have overweight or obesity (Body Mass Index [BMI] ≥ 27 kg/m2). Open-ended concept elicitation (CE) questions allowed participants to discuss the amount of body weight loss needed to have a noticeable improvement on PF. Cognitive tasks were later used during cognitive debriefing (CD) to explore what participants considered a CIC on each PRO measure.

Results: A total of 33 participants were interviewed (mean BMI: 37.6 kg/m2 [27.4 to 56.6 kg/m2] mean age: 45 years [19 to 81 years]). In CE, participants identified 5-10% weight loss as the threshold for having a noticeable improvement on PF and contextualized meaningful weight loss by using real-life examples (e.g., climbing stairs without becoming breathless). In CD, the majority of participants considered a 1-point change at the item level to be indicative of meaningful improvement on both PRO measures.

Conclusions: The combined CE and CD approach facilitated better understanding of meaningful change by participants, providing evidence that a 1-point change, the smallest detectable change on both the SF-36v2 (acute) and IWQOL-Lite-CT, is a CIC in people with overweight or obesity.


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