This is a prospective, observational, multicenter, population-based incidence cohort study which will enroll cases of inflammatory bowel disease IBD (Crohn´s disease CD, ulcerative colitis UC, or indeterminate colitis) diagnosed in adults over 18 months in Spain.

In addition, each incident case that gave his/her informed consent, will be followed up for 12 months to determine changes in phenotype or disease location, the need for immunosuppressive and biologic treatments, and the need for hospital admissions and surgery during the first year after diagnosis.

Also, samples of of blood, urine and stool will be collected during the first year after diagnosis

STUDY DESIGN This is a prospective, observational, multicenter, population-based incidence cohort study which will enroll cases of IBD (CD, UC, or indeterminate colitis) diagnosed in adults over 18 months in Spain.

In addition, each incident case that gave his/her informed consent, will be followed up for 12 months to determine changes in phenotype or disease location, the need for immunosuppressive and biologic treatments, and the need for hospital admissions and surgery during the first year after diagnosis.

Samples of blood, urine and stool will be collected during the study visits.

To achieve the aims this study will be Split in two studies.

1. Epidemiology study to achieve aims 1 and 2.
2. Characterization "omics" study to achieve aims 3, 4 and 5.

CASES DETECION

Case detection In Spain, health care is performed mostly by the public health services. According to recent data, approximately 15% of the Spanish population has private health insurance (Informe Sanidad Privada: Aportando Valor. Análisis de situación 2014 (Report on Private Health Care: Providing Value. 2014 Situation Analysis); available at: https://www.fundacionidis.com/wp-content/informes/informe\_analisis situac_2014_0.pdf). In addition, of those persons having private health insurance, only about 15% make exclusive use of it. For these reasons and taking into account the specific characteristics of IBD, the risk of underestimating the incidence of IBD considering only cases seen in public health centers would be of little relevance. Therefore, this study will be conducted at centers providing public health care within the National Health System.

To conduct this research project, an IBD specialist who is a member of GETECCU has been selected from each Autonomous Community, who will include patients from their health area.

Each participating investigator will confirm the diagnosis at the time of entering patients in the study and 3 months later to assure this diagnosis and the phenotypic characteristics of the disease, and thereby have greater diagnostic accuracy. External monitoring of incident cases included in the registry will also be performed by review of cases selected at random by the research team of Hospital Universitario de la Princesa.

DEFINITIONS

• Disease location and phenotype: IBD location and phenotype will be defined according to the Montreal classification.
• Time to diagnosis: It will be defined as the time from the first medical consultation made by the patient after onset of symptoms to the diagnosis of IBD.
• Population center: The type of population center at the patient's birth and at diagnosis of IBD will be recorded. Whether the population center of origin of the patient is considered rural or urban will be based on the classification of the National Statistics Institute (INE) of each municipality.
• Socioeconomic level: Socioeconomic level will be assessed through different variables, such as the patient's educational level (primary education or lower, secondary education, higher education or equivalent), occupational status (self-employed, employee, unemployed, retired), professional status (nonsalaried or salaried) and type of working hours (full time or part time).
• Number of cohabitants: The number of cohabitants in the patient's home during childhood (up to 16 years) and at diagnosis of IBD will be recorded.
• Smoking: Smoking status will be categorized as "nonsmoker", "smoker", or "ex-smoker", and will be considered at the time of diagnosis of IBD. Patients will be considered "smokers" if they have a smoked more than 7 cigarettes per week for at least 6 months or smoked at least 1 cigarette in the 6 months prior to diagnosis. Patients will be considered "ex-smokers" l if they quit smoking at least 6 months before diagnosis. Patients will be considered "nonsmokers" if they never smoked or did so in a very small amount or occasionally.
• Treatments: Treatments received by the patient in the 12 months since diagnosis of the disease will be included, provided they were received for IBD. Only the first prescription of each therapeutic group will be recorded.
• Changes in phenotype: Changes in phenotype will be considered as the appearance of new lesions not present at diagnosis subsequent to the initial tests performed to determine disease extent and severity. In these cases, the phenotype, the complication leading to classification of the patient in a different phenotype and date of occurrence of the complication will be recorded.
• Hospital admission Hospital admission occurring during the first year from diagnosis of the disease will be included. The date of admission, date of discharge, if related or not to IBD and the cause of admission.
• Surgical procedures: The surgical procedures performed on the patient since diagnosis of IBD (including those performed before knowing the patient had IBD and which led to its diagnosis), the indication for surgery and the date of surgery will be recorded. An emergency surgical procedure will be considered as any surgery performed within 24 from admission of the patient to the emergency department. An elective surgical procedure will be considered as any procedure performed subsequent to the first day of admission and by the usual surgical team.

DATA COLLECTION

Epidemiology study:

Demographic data (age, sex, smoking), family history of IBD, socioeconomic characteristics, IBD type, pattern, and location and presence of extraintestinal manifestations at diagnosis will collected from each patient. The occurrence of complications (fistulas, stenosis, abscesses), changes in disease location, treatments for IBD, surgeries for IBD, and hospital admission during the first year since diagnosis will also be recorded.

Characterization "omics" study Samples of blood, urine and stool. Date of collection and number of samples.

STUDY VISITS

• Visit 0 (baseline): inclusion of patient in the study and collection of socioeconomic data and on diagnosis of IBD. Collection samples of blood, urine and stool.
• Visit 1 (month 3): confirmation of IBD diagnosis and updating of data related to treatment, changes in phenotype, hospital admissions, and surgery. Collection samples of blood, urine and stool.
• Visit 2 (month 12): confirmation of IBD diagnosis and updating of data related to treatment, changes in phenotype, hospital admissions, and surgery. Collection samples of blood, urine and stool. End of study.

Inclusion Criteria:

• Male or female ≥18 years of age diagnosed of inflammatory bowel disease
• Diagnosis of IBD according to European Crohns and Colitis Organisation (ECCO) criteria.
• The patient must belong to the health area of one of the participating center
• Patients who have accepted to participate in the epidemiology study
• < 1 month since the date of the diagnosis colonoscopy

Exclusion Criteria:

• Patients who do not belong to the health area of the participating centers
• Patients who do not accept to participate in the study
• Patients who have initiated a treatment to IBD
• Patients who received a immunomodulators to treat other disease
• Patients with a immune-mediates systemic disease
• Patients with a active infection or a malignancy in the baseline
• Pregnant patients or breastfeeding

Patients recently diagnosed of inflammatory bowel disese who have not initiated a treatment to IBD