Immunochemical fecal occult blood test (iFOBT)
The Immunochemical Fecal Occult Blood Test (iFOBT), also known as the Fecal Immunochemical Test (FIT), is a screening tool designed to detect small amounts of blood in the feces, indicative of potential bleeding in the lower gastrointestinal tract. It is primarily used for screening colorectal cancer, which remains a prevalent and serious health concern despite a decline in incidence attributed to early detection methods. Unlike older tests, the iFOBT specifically targets human hemoglobin, eliminating the need for strict dietary or medication restrictions prior to testing, except for minimizing vitamin C intake shortly before sample collection.
Patients collect their stool samples at home, often over the course of three consecutive days to account for intermittent bleeding. The collection process varies by manufacturer but typically involves using a sampling device to obtain specimens for laboratory analysis. Following a positive result, further diagnostic procedures, such as a colonoscopy, are usually recommended to identify the exact cause of the bleeding. While the test is generally safe, there is a risk of false results due to improper sample handling, underscoring the importance of following collection instructions closely. Overall, the iFOBT plays a crucial role in the early detection and prevention of colorectal cancer, as timely intervention can significantly improve patient outcomes.
On this Page
Subject Terms
Immunochemical fecal occult blood test (iFOBT)
ALSO KNOWN AS: Fecal immunochemical test (FIT)
DEFINITION: An immunochemical fecal occult blood test (iFOBT) is a method for qualitatively detecting a minute amount of otherwise invisible blood in the feces of the lower gastrointestinal tract.
Cancers diagnosed: Colorectal cancers
Why performed: The iFOBT is a screening test for bleeding associated with cancer of the colon and rectum. The bleeding may be attributable to conditions other than cancer, such as polyps and adenomas, which, when discovered and removed early, can significantly reduce the risk of cancer.
Although the incidence of cancer decreased in the United States in the 1980s, colorectal cancer cases increased steadily from the early 1990s through the first decades of the twenty-first century. It remains a common and deadly cancer. The decrease in cases was attributed to screening for fecal occult blood. The immunochemical fecal occult blood test uses an specific for human globins and is more specific than the traditional guaiac test, which detects the heme subunit of mammalian hemoglobin and requires the patient to adhere to dietary and medication restrictions three days before testing.
Patient preparation: The patient collects the specimen at home. No dietary or medication restrictions are required prior to sample collection other than avoiding excessive consumption of vitamin C three days before the test. Blood from hemorrhoids, menstrual blood, or open wounds may invalidate the screening for fecal occult blood. Because bleeding from polyps or other potential lesions is typically intermittent, the patient may be asked to perform collection on three consecutive days.
Steps of the procedure: Two collection procedures are available, depending on which manufacturer provides the diagnostic kit. Both require the patient to follow the instructions provided with the kit.
One company provides a collection paper taped to the toilet seat where feces are deposited. The patient unscrews the sampling device from the collection tube and randomly pierces the specimen with the grooved end of the device in at least five different sites of the feces. The sampler is then screwed into the collection tube and tightened. The patient shakes the tube to mix the specimen with the buffer solution in the collection tube.
The second manufacturer provides two sampling pads that are inoculated with a sampling of toilet water collected after a bowel movement and brushed on the test card provided.
After collection, the sample from either kit is sent to the clinical lab, and the results are reported to the ordering physician.
After the procedure: Positive results are often followed by an endoscopic evaluation such as a colonoscopy.
Risks: One of the risks in iFOBT is a false result due to improper sample collection, as patients may have an understandable aversion to handling a fecal sample. However, an adequate and carefully collected sample is the first critical step in detecting colorectal bleeding, which may be the first sign that the individual is facing the disease. Early detection and treatment are essential in preventing colorectal cancer.
Results: The iFOBT is a screening test. A physician must evaluate and follow positive results to determine the source of the bleeding. Gastrointestinal bleeding may result from diverticulitis, colitis, polyps, or colorectal cancer.
Bibliography
Gearhart, Susan L., and Nita Ahuja. Colorectal Cancer. Saunders, 2010.
Meklin, Jannica, et al. "Fecal Occult Blood Tests in Colorectal Cancer Screening: Systematic Review and Meta-analysis of Traditional and New-generation Fecal Immunochemical Tests." Anticancer Research, vol. 40, no. 7, 2020, pp. 3591-3604. doi.org/10.21873/anticanres.14349.
Seed, Shawna. "Fecal Occult Blood Test: Everything You Should Know." WebMD, 5 Apr. 2024, www.webmd.com/digestive-disorders/digestive-diseases-stool-testing-blood-fecal-occult-blood-test. Accessed 20 June 2024.
Syed Soffian, Sharifah S., et al. "Rate and Associated Factors of Refusal to Perform Immunochemical Faecal Occult Blood Test (iFOBT) Among Semi-urban Communities." Plos one, vol. 16, no. 10, 2021. doi.org/10.1371/journal. pone.0258129.
Talley, Nicholas J., et al. Gastroenterology and Hepatology: A Clinical Handbook. Elsevier, 2008.
Vannelli, Alberto. Colorectal Cancer. IntechOpen, 2021.