Psychometric testing of the ICECAP-A in patients with coeliac disease: a comparative analysis with EQ-5D-5L.

OBJECTIVES: This study aimed to assess the psychometric properties of the ICEpop CAPability measure for Adults (ICECAP-A) in patients with coeliac disease (CD) and compare its performance with EQ-5D-5L. METHODS: An online cross-sectional survey was conducted among 312 adult patients with CD in Hungary, who completed both the ICECAP-A and EQ-5D-5L. Psychometric properties assessed included distributional characteristics, convergent validity with the Gastrointestinal Symptom Rating Scale (GSRS), Satisfaction with Life Scale (SWLS), and known-group validity. RESULTS: Mean age was 35.8 years (range: 18-80), and 70.2% were female. On the ICECAP-A, 51% (attachment) to 81% (stability) of patients reported limitations, while on the EQ-5D-5L, 2% (self-care) to 41% (pain/discomfort) reported problems. Ceiling effect was not observed for the ICECAP-A (6.7%), but reached 38.8% for EQ-5D-5L. The mean index value was 0.85 for the ICECAP-A and 0.92 for the EQ-5D-5L. ICECAP-A correlated strongly with SWLS (r=0.698), moderately with EQ-5D-5L (r=0.551) and weakly with GSRS (r=-0.284). Both the ICECAP-A and EQ-5D-5L were able to differentiate between known groups based on general health status and relevant clinical variables (e.g. symptoms, comorbidities, duration on gluten-free diet and adherence to it); however, the EQ-5D-5L typically showed somewhat larger effect sizes. CONCLUSION: This study is the first to validate ICECAP-A in patients with CD, demonstrating good psychometric performance, including strong convergent and known-group validity. Its ability to capture broader aspects of well-being supports its use as a valuable tool in outcome assessments for this patient population.