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Fecal immunochemical test (FIT)

Definition

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.

Alternative Names

Immunochemical fecal occult blood test; iFOBT; Colon cancer screening - FIT

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 pubmed.ncbi.nlm.nih.gov/28555630/.

US Preventive Services Task Force website. Final recommendation statement. Colorectal cancer screening. www.uspreventiveservicestaskforce.org/uspstf/recommendation/colorectal-cancer-screening. Published May 18, 2021. Accessed August 9, 2023.

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 pubmed.ncbi.nlm.nih.gov/29846947/.

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