Fecal Immunochemical Test (FIT)
Put simply, the fecal immunochemical test, or FIT, tests the stool for blood to determine if a more comprehensive examination is necessary. Occult, or hidden, blood is a critical symptom in the detection of precancerous polyps or colon cancer. This test is a relatively new addition in the fight against colorectal cancer, the third leading cause of death in the United States, according to the Centers for Disease Control and Prevention. FIT is easier to take and more accurate than older tests like the fecal occult blood test, or FOBT.
What is FIT used for?
FIT is a screening tool for colon cancer and lower intestinal bleeding. Fecal occult blood is not visibly apparent, so patients have it without knowing it’s there. The goal of FIT is to detect subtle blood loss due to gastrointestinal tract bleeding. Stool positive for occult blood warrants further investigation, such as an anoscopy looking for polyps or signs of malignancy.
Patients with obvious blood in the stool or with active bleeding due to anal fissure or hemorrhoid will not benefit from this test. Woman having their menstrual periods or a person with blood in the urine will register false positives with FIT, as well.
FIT is a Self-Test
FIT is a self-test a patient performs at home. That makes it a more comfortable option than anoscopy or other types of examinations. The patient receives a kit for collection of the stool sample. They should be instructed to remove any automatic toilet cleaning devices or solutions before collecting their sample.
After a bowel movement, the patient brushes the surface of fecal matter with the collection tool from the kit. The sample is placed on a test card following the instructions provided. One to three samples are required for each test depending on the sensitivity level. Each sample gets a separate test card and should come from a different bowel movement. Once samples are collected and placed on the cards, the patient seals them into an envelope and returns the kit to the doctor or lab. The assigning physician will have test results within a few days. A positive FIT indicates the need for anoscopy examination and further testing.
Unlike the traditional guaiac FOBT, FIT has no dietary restrictions. Food intake and supplemental vitamins will have no effect on the test results. This means sample collection is less complicated for the patient than the gFOBT.
Who Should Take This Test
There is no patient risk associated with the Fecal Immunochemical Test, so it is safe for anyone. Patients over the age of 50 should have a test done at regular intervals even if there is no family history of colorectal cancer. FIT is more accurate that other tests, so it is the ideal choice for younger patients who are at risk for peptic ulcer or colon disease, as well.
Unlike the gFOBT, which is often riddled with false positives, a positive FIT indicates the presence of occult blood in the stool. Infection and red meat will not alter this test as they do with its predecessors. This means, in the absence of menstrual blood or blood in the urine, a positive FIT is a definite indicator of bleeding in the lower digestive tract. Such a result would require further investigation including anoscopy.
Occult blood in the stool can be the first warning sign of colorectal cancer. The Fecal Immunochemical Test provides physicians with a more comprehensive tool to detect it.