Prospective study to test whether the immunochemical fecal occult blood test (FIT) for colorectal cancer (CRC) helps to prioritize patients with iron deficiency anemia for colonoscopy.

This is a multicenter (two centers), prospective study to test the accuracy of FIT for CRC detection in patients with severe IDA and its potential value for prioritizing colonoscopy.

An appointment with a gastroenterologist will be scheduled for patients with IDA referred for upper gastrointestinal endoscopy or colonoscopy. The gastroenterologist will check the inclusion and exclusion criteria. Eligible patients will sign the informed consent to carry out the following procedures:

1. Blood analysis to rule out celiac disease (anti-transglutaminase IgA antibodies and IgA).
2. A quantitative fecal immunological test (FIT: OC-Sensor ®) will be provided.
3. An appointment for colonoscopy and gastroscopy will be provided after completion of the FIT in all patients. During gastroscopy, duodenal biopsies from the second portion of the duodenum and duodenal bulb will be taken to rule out celiac disease. Biopsies from the stomach will be also taken to assess helicobacter pylori infection.
4. In patients with severe anemia colonoscopy and upper endoscopy will be prioritized (<20 days) (primary outcome).
5. Patients with colonoscopy and gastroscopy without significant lesions, will be scheduled for the performance of a capsule endoscopy.
6. Endoscopists will be blind for the FIT results.
7. the following information will be collected: consumption of acetylsalicylic acid, non steroidal anti inflammatory drugs, oral anticoagulants, corticosteroids and proton pump inhibitors (PPI). In the case of patients receiving treatment with PPIs, they will be removed 15 days before the completion of the FIT and not resumed until the performance of the upper endoscopy.

The hypothesis of the study is that one-time FIT is a useful tool for increasing the efficiency of colonoscopy and can be used to prioritize outpatient colonoscopy in patients with IDA. In order to calculate the sample size required for the study, the investigators have assumed that FIT is positive in 25% of cases with iron deficiency anemia and 20% of them would have an advanced colorectal neoplasia at colonoscopy whereas only 10% of advanced colorectal neoplasias would be found in the remaining 75% patients with a negative FIT. Considering a type I error (alpha) of 5%, a power of 80% and a percentage of losses of 15%, 550 patients will be necessary to include. The investigators estimate that approximately 15% of these patients (n=83) will have severe anemia.

Inclusion Criteria:

• Consecutive outpatients with iron deficiency anemia (Hemoglobin < 13 g/dl in males and 12 g/dl in females) referred for upper endoscopy and/or colonoscopy.
• To sign the informed consent.

Exclusion Criteria:

• < 18 years
• Pregnancy
• Personal history of inflammatory bowel disease
• Gastric / duodenal ulcer or gastrointestinal neoplasia
• Family history of hereditary CRC (Lynch Syndrome or familial adenomatous polyposis)
• Rectal bleeding / hematochezia
• Gastroscopy / colonoscopy / endoscopy capsule in the previous 5 years
• Patients not candidates for endoscopic studies because a low performance status
• Previous abdominal surgery
• Refusal to participate.