BACKGROUND: In the complex etiology of inflammatory bowel disease (IBD), the exposome is a major contributor. Though many environmental exposures have been identified, quality of evidence varies greatly and overall evidence for the exposome is inconclusive. A universal, precise, and reproducible measurement tool is needed to study the exposome in IBD.
METHODS: We built the web-based Groningen IBD Environmental Questionnaire (GIEQ), an extensive and structured questionnaire measuring potentially involved environmental exposures, consisting of 848 items, subdivided into 15 categories. For validation, 76 IBD patients completed the GIEQ twice (2-month interval). Cohen's kappa and correlation coefficients were used to compare both fills. Internal consistency was evaluated using Cronbach's alpha tests. Proportional bias was examined using Bland-Altman plots.
RESULTS: In general, we obtained a mean kappa coefficient of 0.78 (standard deviation 0.17) for categorical questions and a mean intraclass correlation coefficient of 0.88 (0.15) for numeric questions. Cronbach's alpha ranged from 0.64 to 1.0 with a mean of 0.79 (0.14). Bland-Altman plots showed proportional bias only for current physical activity score.
CONCLUSIONS: The GIEQ is a reliable measurement tool to study the exposome in IBD, enabling consistent measurement of an extended number of environmental factors and their interactions. Use of the GIEQ across IBD cohorts will lead to more standardized, generalizable, and comparable results. Also, the GIEQ can be used for calculation of an exposome risk score, applicable for secondary prevention by identifying high-risk patients as well as to analyze interactions between the exposome and other aspects of IBD etiology.