Fecal Occult Blood Test

This non-invasive test can help determine if there is blood in your stool

Stool Test Results
A stool test can be used to determine if there is blood in your stool. Image © sunil menon / E+ / Getty Images

What Is It?

A fecal occult blood test (also called stool guaiac or hemoccult test) is used to examine stool for traces of blood that can not be seen with the naked eye. This test can detect bleeding that is coming from almost anywhere in the digestive tract. A positive result could be due to intestinal bleeding caused by one of several conditions, including colorectal cancer, esophagitis, gastritis, stomach cancer, ulcerative colitis and hemorrhoids.

This test may also give a positive result when asprin or other medications that irritate the digestive tract have been taken.

What Is It Used For?

A fecal occult blood test is often used to dectect colorectal cancer in its early stages, because the disease may have no other signs or symptoms early in its course. Fecal occult blood tests are usually recommended annually for people over 50 years old who are not using another screening method (such as colonoscopy). In some cases, it's recommended that people at high risk for colorectal cancer because of family history or polyps begin testing at age 40. In other cases, it's recommended that people be tested at an age 10 years younger than the age their family member was at the diagnosis of colon cancer.

What Is The Preparation?

Having current bleeding for a known reason will give a positive result. Therefore, you should not test if you:

  • Have blood in your urine
  • Have taken asprin or other nonsteroidal anti-inflammatory drugs (NSAIDs) in the past 7 days
  • Are a woman having your menstral period or during the first three days after the end of your period

At least 72 hours before the test, make the following changes to supplements and diet:

  • Avoid taking more than 250 mg/day of vitamin C
  • Avoid eating red meat (beef or lamb), including liver and processed meats or "cold cuts"
  • Avoid eating raw fruits and vegetables, especially melons, radishes, turnips, and horseradish

Any toilet bowel cleansers should be removed from the toilet, as the chemicals can affect the results of the test.

How Is It Done?

You will be given a kit to be used for collecting stool samples for the test. This kit should be kept in the bathroom at home, or carried with you when you're away from home during the three day test. Be sure to write your name and other information on the collection slides.

Flush the toilet twice before a bowel movement. Use one of the small wooden sticks from the kit to collect a sample of stool from the toilet. Apply the sample to the correct space on the sampling slide. Repeat for two more days or two more bowel movements as directed by your doctor. Cover the slides and store them away from heat, light, and strong chemicals.

After completing the test, seal the test envelope and return the kit to your doctor or to the laboratory.

What Are The Risks?

This test is safe and painless.

Is A Follow-up Necessary?

Call your doctor in a few days for the results.

When a test returns a positive result (which indicates that there could be bleeding in the digestive tract), additional procedures such as a sigmoidoscopy or a colonoscopy may be recommended.

When Should I Call The Doctor?

Call your doctor if you have diarrhea or constipation during the test period.

Anything Else I Should Know?

Read all instructions carefully before testing begins to ensure that the test is as accurate as possible.

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