Immunological Characteristics of Preclinical IBD

Inclusion criteria

Patients from cohort A will be included if they fulfill all the following inclusion criteria:

* Male or female ≥18 years of age at baseline.
* New diagnosis of IBD during a CRC screening colonoscopy, based on the criteria from the European Crohn's and Colitis Organization (33, 34).
* Presence of a chronic inflammatory infiltrate and histological diagnosis compatible with IBD.
* The patient must be asymptomatic at diagnosis and without previous symptoms suggestive of IBD.
* Time interval between the index colonoscopy and the baseline visit up to 3 months.

Patients from cohort B will be included if they fulfill all the following inclusion criteria:

* Male or female ≥18 years of age at baseline.
* Recent diagnosis of IBD, with <3 months from symptoms onset.
* Time interval between the index colonoscopy and the baseline visit up to 3 months.

Patients from cohort C will be included if they fulfill all the following inclusion criteria:

* Male or female ≥18 years of age at baseline.
* No endoscopic signs of IBD after a complete ileo-colonoscopy within the CRC screening program.
* Time interval between the index colonoscopy and the baseline visit up to 3 months.

Exclusion criteria

Patients from cohort A will be excluded if they fulfill any the following exclusion criteria:

* Identification of any enteropathogen in the stool culture.
* Isolated findings of acute inflammatory infiltrate without signs of chronicity.
* Previous or current diagnosis of microscopic colitis.
* Alteration in biomarkers in blood or stool will not constitute an exclusion criterion.

Patients from cohort B will be excluded if they fulfill any the following exclusion criteria:

\- Previous use of immunomodulators or biologics for any condition.

Patients from cohort C will be excluded if they fulfill any the following exclusion criteria:

* Any gastrointestinal symptoms at baseline.
* Previous use of immunomodulators or biologics for any condition.