Fecal immunochemical test (FIT)
Immunochemical fecal occult blood test; iFOBT; Colon cancer screening - FIT
The fecal immunochemical test (FIT) is used as a screening test for colon cancer. It tests for hidden blood in the stool, which can be an early sign of cancer. FIT only detects human blood from the lower intestines. Medicines and food do not interfere with the test. So it tends to be more accurate and have fewer false positive results than other tests.
Colon cancer is one of the leading causes of cancer-related deaths in the United States. The good news is that earlier diagnosis due to screening tests often leads to a complete cure. Colorectal cancer starts in the large intestine, also known as the colon. Nearly all colon cancers begin as noncancerous, or benign, polyps, some of which may slowly develop into cancer. Screening can detect these polyps and early cancers. Polyps can be removed years before cancer even has a chance to develop. Your doctor can use two types of tools to screen for cancer. The first type is a stool test. Polyps in the colon and small cancers can bleed tiny amounts of blood that you can't see with the naked eye. The most common method to test for the presence of blood is the fecal occult blood test or FOBT. This test checks your stool for small amounts of blood that you may not be able to see. Two other stool tests are the fecal immunochemical test and the stool DNA test. The second type of screening tests involve looking at the lining of the colon. One of these tests is a sigmoidoscopy exam. This test uses a flexible scope to look at the lower portion of your colon. But, because it looks only at the last one-third of the large intestine, it may miss some cancers. So this test is done along with a stool test. A colonoscopy is similar to sigmoidoscopy, but it can see the entire colon. For this test, your doctor will give you instructions for cleansing your bowel. This is called bowel preparation. During the colonoscopy, you’ll receive medicine to make you relaxed and sleepy. Another test your doctor may recommend is a virtual colonoscopy, also called a CT colonography. This test uses a CAT scan and computer software to create a 3-D image of your large intestine. Beginning at age 45, all men and women should have a screening test for colon cancer. Screening options for people with average risk for colon cancer include visual based exams. These could be a colonoscopy every 10 years starting at age 45 or a virtual colonoscopy every 5 years. A Flexible sigmoidoscopy every 5 years or a Flexible sigmoidoscopy every 10 years plus stool testing with FIT done every year. Screening options also include stool based tests. People with average risk should have an FOBT or FIT every year. A colonoscopy is needed if the results are positive, or a Stool DNA test every 1 to 3 years. A colonoscopy is needed if the results are positive. People with certain risk factors for colon cancer may need screening at a younger age, or they may need screening more often. Such people include those with a family history of colon cancer, those with a history of previous colon cancer or polyps, or people with a history of ulcerative colitis or Crohn disease. The death rate for colon cancer has dropped in the past 15 years and this may be due to increased awareness and colon screening. In general, early diagnosis is much more likely to lead to a complete cure.
How the Test is Performed
For colon cancer screening, you will be given the test to use at home. Be sure to follow the instructions provided. Most tests have the following steps:
- Flush the toilet before having a bowel movement.
- Put the used toilet paper in the waste bag provided. Do not put it into the toilet bowl.
- Use the brush from the kit to brush the surface of the stool and then dip the brush into the toilet water.
- Touch the brush on the space indicated on the test card.
- Add the brush to the waste bag and throw it away.
- Send the sample to the lab for testing.
- Your health care provider may ask you to test more than one stool sample before sending it in.
How to Prepare for the Test
You do not need to do anything to prepare for the test.
How the Test will Feel
Some people may be squeamish about collecting the sample. But you will not feel anything during the test.
Why the Test is Performed
Blood in the stool may be an early sign of colon cancer. This test is performed to detect blood in the stool that you cannot see. This type of screening can detect problems that can be treated before cancer develops or spreads.
Talk with your provider about when you should have colon screenings. If you are age 45 to 75, you should be screened for colorectal cancer. There are several screening tests available:
- A stool-based fecal occult blood (gFOBT) or fecal immunochemical test (FIT) every year
- A stool sDNA test every 1 to 3 years
- Flexible sigmoidoscopy every 5 years or every 10 years with stool testing by FIT done every year
- CT colonography (virtual colonoscopy) every 5 years
- Colonoscopy every 10 years
Normal Results
A normal result means the test did not detect any blood in the stool. However, because cancers in the colon may not always bleed, you may need to do the test a few times to confirm that there is no blood in your stool.
What Abnormal Test Results Mean
If the FIT results come back positive for blood in the stool, your provider will want to perform other tests, usually including a colonoscopy. The FIT test does not diagnose cancer. Screening tests such as a sigmoidoscopy or colonoscopy can also help detect cancer. Both the FIT test and other screenings can catch colon cancer early, when it is easier to treat.
Risks
There are no risks from using the FIT.
References
Garber JJ, Chung DC. Colonic polyps and polyposis syndromes. In: Feldman M, Friedman LS, Brandt LJ, eds. Sleisenger and Fordtran's Gastrointestinal and Liver Disease. 11th ed. Philadelphia, PA: Elsevier; 2021:chap 126.
Lawler M, Johnston B, Van Schaeybroeck S, et al. Colorectal cancer. In: Niederhuber JE, Armitage JO, Kastan MB, Doroshow JH, Tepper JE, eds. Abeloff's Clinical Oncology. 6th ed. Philadelphia, PA: Elsevier; 2020:chap 74.
Rex DK, Boland CR, Dominitz JA, et al. Colorectal cancer screening: recommendations for physicians and patients from the U.S. Multi-Society Task Force on Colorectal Cancer. Am J Gastroenterol. 2017;112(7):1016-1030. PMID: 28555630
US Preventive Services Task Force website. Final recommendation statement. Colorectal cancer screening.
Wolf AMD, Fontham ETH, Church TR, et al. Colorectal cancer screening for average-risk adults: 2018 guideline update from the American Cancer Society. CA Cancer J Clin. 2018;68(4):250-281. PMID: 29846947
Version Info
Last reviewed on: 8/8/2023
Reviewed by: Michael M. Phillips, MD, Emeritus Professor of Medicine, The George Washington University School of Medicine, Washington, DC. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
