Instructions for Occult Blood Testing

Since colon cancers may bleed only intermittently, the test for blood in the stool is done on 3 different bowel movements. This may increase the chance of detecting trace amounts of blood in your stool.

To increase the accuracy of the test, you should make some simple diet changes at least 2 to 3 days before starting the test and continue them until you have collected all 3 stool samples.

In the days before you perform the fecal occult blood test (FOBT), be sure to eat plenty of:

• Vegetables, especially lettuce, spinach, and corn.
• Fruits, especially apples, prunes, and grapes.
• Cereals or breads that contain bran.

Before doing an FOBT, try to avoid:

• Turnips, radishes, and horseradish, since these foods can cause misleading test results (false-positive test results). Also avoid red meat for several days because blood in the meat may cause misleading test results. Small amounts of chicken, turkey, or fish will not interfere with test results.
• Iron supplements.
• Aspirin (or products that contain aspirin) and anti-inflammatory medications (NSAIDs).
• Vitamin C supplements.

Do not perform the test during your menstrual period or if you have active bleeding caused by hemmoroids. Also, do not test a stool sample that has been in contact with toilet bowl cleaning products that turn the water blue.

How It Is Done

The procedure requires you to obtain two small amounts of stool and apply them to small areas of blotter paper on a test slide. Usually the doctor will order a series of three, so you will use stool samples from 3 different bowel movements. Testing may take from one to several days, depending upon how often you have a bowel movement. During the time you are collecting the samples, you should continue the diet as outlined above.

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