Towards Standardization of CGM Performance Studies: The QUSS-CGM Questionnaire for Assessing User Satisfaction

User satisfaction and ease of use of continuous glucose monitoring (CGM) systems are key factors in patients' device acceptance. CGM user satisfaction is often assessed through questionnaires, but item selection varies widely across studies. The aim of this study was to design, develop and validate a Questionnaire for User Satisfaction Standardized for CGM performance studies (QUSS-CGM).

Selection of attributes and design of questionnaire items was based on a systematic literature search of publications on CGM performance evaluation studies. Content and response process validation of a draft-questionnaire was performed by experts (n=9) and people with diabetes (n=10), respectively. The resulting German pre-QUSS-CGM questionnaire underwent validation in two CGM performance studies ("pilot" studies) performed between June and August of 2024, via a pooled psychometric evaluation (exploratory factor analysis (EFA) and reliability) of n=126 questionnaires from these studies, followed by bidirectional translation to English.

Two hundred and five items on user satisfaction in CGM performance studies were identified by systematic literature search and classified into six attributes according to their content. Items were summarized in a 25-item draft-questionnaire on a 5-point Likert scale. Content and face validity were considered acceptable with a scale-level content validity index (S-CVI/Ave) of 0.90 and a scale-level face validity index (S-FVI/Ave) of 0.93, both based on the average method. EFA revealed a two-factor structure for the final QUSS-CGM questionnaire summarized to 11 items, demonstrating high internal consistency (Cronbach's α of 0.84).

The QUSS-CGM was designed, developed, and validated as a reliable and standardized tool to measure user satisfaction in CGM performance evaluation studies.