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Fecal Occult Blood Test

(FOBT)

Pronounced: Fee-kal Uh-kult Blood Test

What Is Occult Blood?

Occult blood is blood in your feces that cannot be seen by the eye. It can be caused by bleeding in the body between your stomach and anus.

Reason for the Test

This test is done to find colon cancer at an early stage. It can also be used to find blood in your stool if you are having belly pain, diarrhea, vomiting, lack of hunger, or other problems.

The test may be needed as a routine screen for colon cancer for people who are at risk. Men and women should be screened every year after age 50. People with a personal or family history of polyps or colon cancer should be screened earlier.

The test may also be done if your doctor thinks that you have an intestinal infection or swelling.

Type of Sample Taken

A small sample of your stool is needed.

Prior to Collecting the Sample

  • There are some medicines and foods you should not have before the test, such as:
    • Nonsteroidal anti-inflammatory drugs (NSAIDs) should not be used for 7 days before the test. If you are taking them for health problems, talk to your doctor before you stop taking them.
    • Red meats, cantaloupe, uncooked veggies, blood sausage, and hot sauce should not be eaten for 3 days before the test
  • People with hemorrhoids should wait to have the test until they are not bleeding.
  • Do not have the test during your menstrual period.
  • Do not clean your toilet bowl for several days before the test. Chemicals from cleaners can affect the test.

During the Sample Collection

The sample can be taken by a doctor in the office or at home using a kit. The kit is the preferred method.

If your doctor takes the sample in the office, you will be asked to lower your pants and bend over. The doctor or nurse will wear gloves. A small sample of stool will be taken during a digital exam. This is a quick test with little pain.

You may also be given a kit to collect a sample at home. When you are ready to have a bowel movement, you will set up the kit according to the instructions. The kit should let you to collect 3 samples of stool within a week. Some kits have a disposable container into which you can pass your bowel movement. Other kits might have paper or plastic wrap that you can lay in the toilet to help keep your stool from getting in the water.

Use the thin wooden sticks in the kit to pick up a small amount of stool and smear it onto the card. People who do not have hemorrhoids may be allowed to smear the stool onto the card with stool from toilet paper. Seal and return the samples to the office.

After Collecting the Sample

You will not have any problems from this test.

Results

It will take several days to get your results.

Only about half of colon cancer tumors shed enough blood to be found on this test. Blood in your stool can be from:

  • Colon polyps
  • Diverticular disease
  • Hemorrhoids
  • Anal fissures
  • Inflammation from health problems, such as gastritis, erosive esophagitis, celiac disease, inflammatory bowel disease, and ischemic bowel disease
  • Vascular problems, such as esophageal varices or angiodysplasia of the gastrointestinal tract
  • Infections, such as tuberculosis, hookworm, whipworm, and amebiasis
  • Ulcers

Talk to your doctor about your test results. A test may point to an illness that you do not have. It can also miss an illness that you may have. The doctor will check your symptoms and all test results before making a diagnosis.

REFERENCES:

Colorectal cancer screening. EBSCO DynaMed website. Available at:http://www.dynamed.com/topics/dmp~AN~T114074/Colorectal-cancer-screening. Updated November 30, 2018. Accessed May 21, 2019.

Last reviewed March 2019 by EBSCO Medical Review BoardJames P. Cornell, MD  Last Updated: 5/21/2019