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.