An Epidemiological Study of the Incidence of Inflammatory Bowel Disease in Spain

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 1 year 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.

Study population Incident cases diagnosed with IBD over 12 months in the Spanish territory, which has a population of 46,439,864 inhabitants (1 January 2015) according to data from the National Statistics Institute (INE). According to recent data, only 3% of incident cases are diagnosed in the pediatric population, so the study will focus on adult patients (over 15 years of age).

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.

Furthermore, as previously mentioned, according to recent data only 3% of incident cases are diagnosed in the pediatric population, so the study will focus on adult patients (over 16 years of age)4.