Psychometric validation of the celiac disease-specific quality of life survey (CD-QOL) in adults with celiac disease in the United States

PURPOSE: Celiac disease and its treatment negatively impact quality of life, indicating potential need for measurement of disease-specific quality of life domains to inform interdisciplinary intervention. The Celiac Disease Quality of Life Survey (CD-QOL) has been used in clinical research; however, its factor structure has not been confirmed and psychometric properties have not been evaluated in English-speaking adults in the U.S. Aims: (1) Confirm the factor structure of the 20-item English CD-QOL; (2) assess psychometric properties including internal consistency reliability, convergent validity, known groups validity, and incremental validity. METHODS: 453 adults with self-reported Celiac disease (M(age) = 40.57; 88% female; 92% White) completed the CD-QOL and validated measures of generic health-related quality of life (SF-36), gluten-free diet adherence (CDAT), anxiety and depression symptoms (PROMIS), and physical symptoms (CSI) as part of the iCureCeliac(®) patient-powered research network. RESULTS: Confirmatory factor analysis found superior fit for a bifactor structure with one general factor and four group factors. Ancillary bifactor analyses suggest the CD-QOL can be considered primarily unidimensional. Total and three subscale scores demonstrated acceptable internal consistency reliability. Convergent and known groups validity were supported. The CD-QOL demonstrated some incremental validity over the SF-36. CONCLUSION: The English CD-QOL can be used as a measure of disease-specific quality of life among adults with Celiac disease in the U.S. Compared to generic instruments, the CD-QOL appears to better capture specific cognitive and affective aspects of living with Celiac disease. Use of a total score is recommended. Its utility as a screening and outcome measurement tool in clinical settings should be examined.