An early treatment of inflammatory bowel disease (IBD) has been proposed to correlate to better outcomes. In Catalonia the screening programme was implemented in all the territory in 2015. The aim of this study is to describe the natural history of the asymptomatic IBD detected during colorectal cancer population screening.

This study will be performed and reported according to the STROBE Statement guidelines ( http://www.strobe-statement.org/index.php?id=strobe-home).

Design:

Observational, multicentre and retrospective cohort study.

Centre selection and recruitment:

All the participating centres in population colorectal cancer screening in Catalonia will be invited. All the participating centres must certify the approval of the protocol in their ethical committees.

Study population:

All patients with asymptomatic IBD diagnosed during the population colorectal cancer screening in the Catalonian colorectal screening program within the period 2000 to 2019 will be included.

Study variables

Prevalence of asymptomatic IBD diagnosed and their evolution through the years will be described. The following variables will be collected (annex1):

• Sex (male, female)
• Age
• Fecal immunotest (value)
• Date of screening colonoscopy (yyyy/mm/dd)
• Ileoscopy performed (yes/no)
• Type of IBD (CD, UC, indeterminate colitis)
• Endoscopic findings: mild-moderate activity or severe activity for CD and Mayo score for UC (value of the scores).
• Montreal classification (value of the classification)
• Histology (diagnostic, compatible, unspecific or no compatible)
• Microscopic description (cryptitis, abscess, mucus depletion, granuloma, architectural pattern alteration
• Past medical history, smoking habit, previous abdominal surgeries and comorbidities.
• Familiar history of IBD
• Extraintestinal manifestations (cutaneous, ophthalmologic, articular)
• Other studies performed (endoscopic capsule, MRI, gastroscopy, echography).
• Calprotectin: value of the first analysis in the outpatient visit.
• Blood test: Haemoglobin, ferritin and PCR: values of the first analysis in the outpatient visit.
• Fist symptom: none, change in depositional rhythm, abdominal pain, weight loss, rectal urgency, anal pain, iron deficiency anaemia.
• Date of first IBD symptom (yyyy/mm/dd)
• Time to first IBD symptom: time in days from the diagnosis of IBD.
• Treatments used: none; 5- aminosalicylates, corticosteroids, non-biologic immunosuppressive treatment, biologic treatment, surgery
• Treatment start and end date (yyyy/mm/dd)
• Time to first treatment: time in days from the diagnosis of IBD.
• Follow-up endoscopy: Date (yyyy/mm/dd) and activity.

Data collection:

All patients with asymptomatic IBD diagnosed during the population colorectal cancer screening within the period 2000 to 2019 will be identified by the colorectal cancer screening program registry.

Patient identity will be given to a data manager. This manager will administrate the data of each patient in their hospital.

The person in charge of the study in each hospital will collect the anonymized data using REDCap database (Research Electronic Data Capture), a secure, web-based application designed to support data collection form research studies.

Statistical methods:

Categorical variable will be given as natural frequencies and percentages and quantitative variables will be given as mean or median and standard deviation or interquartile ranges. Kaplan-Meier analysis will be used to describe the time to first symptom and or time to first treatment. If necessary, the long rank test will be used to compare survival curves. A multivariate Cox analysis will be performed to ascertain the independent predictors of aggressive disease.

Ethical issues:

The research will use retrospective anonymized data from the technical screening office of Catalonia. No personal data will be used, and all the patient data will be encrypted, so that no personal identification would be retrievable or traceable to the original source from the working database.

All the researchers who collaborate in the study will sign a commitment document in which their functions and obligations will be defined. Both in the collection of data and in the analysis, Organic Law 3/2018, of December 5, on the Protection of Personal Data and guarantee of digital rights and the provisions of European Regulation 679/2016 will be followed.

The study was revised and approved by the local ethics committee of the Hospital universitarian Parc Tauli in Sabadell (CEIC 2021/5006) on 15 February 2021. The study will comply with the ethical guidelines of the Declaration of Helsinki. Therefore, as the study uses retrospective anonymized data and it has no impact on evolution or treatment patient, there is no need to obtain informed consent. The study will be performed in accordance with the STROBE statement for reporting observational studies in Epidemiology.

Inclusion Criteria:

• All patients with asymptomatic IBD diagnosed during the population colorectal cancer screening in the Catalonian colorectal screening program within the period 2000 to 2019 will be included.

Exclusion Criteria:

• Symptoms in the first outpatient visit.

Centre selection and recruitment:

All the participating centres in population colorectal cancer screening in Catalonia will be invited. All the participating centres must certify the approval of the protocol in their ethical committees.

Study population:

All patients with asymptomatic IBD diagnosed during the population colorectal cancer screening in the Catalonian colorectal screening program within the period 2000 to 2019 will be included.