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Fecal Occult Blood Test

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What is the test?

This test detects blood in your stool, which can be a sign of bleeding anywhere from your nose and mouth to your rectum, such as from an ulcer, a polyp, or cancer. If you're over 50, you should have this test annually during the years when you don't have either a colonoscopy or sigmoidoscopy to screen for colon cancer. Keep in mind, however, that both colonoscopy and sigmoidoscopy are better at detecting cancer than a fecal occult blood test.

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How do I prepare for the test?

If the traditional test is used, you collect samples of your stool at home and send them to a laboratory or clinic for analysis. Your doctor gives you a kit with all of the materials you need. A newer test uses flushable pads to detect blood in the toilet bowl following a bowel movement, so that no stool samples are required.

For several days before taking the samples, you must avoid medicines that can interfere with the results. These include NSAIDs and blood thinners (see "Medication precautions," page 35) which can cause minor stomach bleeding, thereby giving an abnormal test result. If you have hemorrhoids, wait until they stop bleeding before doing the test. Women shouldn't collect stool samples near the time of menstruation. Finally, avoid using toilet bowl cleaners for several days before the test, because these chemicals can affect the results if they come in contact with your stool sample.

For several days before the test, you also need to avoid foods and vitamins that can affect the test result. Foods to avoid include red meat (the blood it contains can turn your test positive), radishes, turnips, cabbage, cauliflower, horseradish, uncooked broccoli, and cantaloupe (all of which contain a chemical that can turn the test positive), and citrus fruits and vitamin C supplements (which can turn the test falsely negative).

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What happens when the test is performed?

If one of the traditional tests is used, you collect three stool samples, ideally on three different days. Some kits include tissue paper that you can lay on the surface of the toilet bowl water to help keep the stool sample from sinking. As an alternative, you can pass your bowel movement into a disposable container. Once you've had a bowel movement, obtain a very small sample of the stool using the thin wooden sticks in your kit and smear it on a card from your kit. Then fold over the card to protect your sample.When you have all three samples, mail the cards to the clinic or lab in the plastic-lined envelope given to you.Make sure that your name is written on each card.

In the lab, the cards are treated with a chemical that produces a blue color when blood is present in the sample. This test works fine no matter how long it took your samples to reach the lab.

If you have the flush pad test, you drop the pad into the toilet bowl after you've had a bowel movement, for three consecutive days. The pads change color when blood is present in the toilet bowl. You can flush the toilet to dispose of the pads, but-if blood is detected-should contact your doctor.

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What risks are there from the test?


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Must I do anything special after the test is over?


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How long is it before the result of the test is known?

With the flush pad method, results are available immediately.With the more traditional methods, testing is performed in only a few minutes once the lab receives your sample. Some clinics or labs do this testing in batches and wait to process the test until samples have been received from several people. You should hear from your doctor's office within a week after the lab has received your specimen. If your test is positive, it means you have blood in your stool, and your doctor will recommend some additional testing to find out the cause.

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