Description of the test

Checking the stool (feces) for blood helps doctors make a diagnosis. Occult blood means that blood is "hidden" in the stool and therefore is not necessarily visible. The blood is detected using chemical analysis. Blood in the stool may indicate various conditions including inflammatory bowel disease (IBD), ulcers, hemorrhoids, or colon cancer.

How often should the test be performed?

The frequency of this test is determined by your doctor. Testing is recommended every one to two years for people over 50 years of age to screen for colorectal cancer. More frequent testing or testing at an earlier age may be recommended if you are at an increasted risk of colorectal cancer (e.g., if you have a family history of colon cancer).

Why is this test performed?

Doctors often request this test to screen for colorectal cancer for people over 50 years of age. The test is also occasionally ordered to help diagnose other problems in the digestive tract.

Are there any risks and precautions?

There are very few health risks for this test. However, dealing with stool may be a difficult experience for some people. Try to follow instructions closely and do things slowly to avoid problems. Wash your hands before and after collecting the sample.

What happens during the test?

Two different tests look for blood in stool: the flushable reagent pad and the guaiac smear test.

Flushable reagent pads do not require that you handle stool directly. Instead, you place the pad in the toilet after your bowel movement, and then check for colour changes on the pad. You can buy flushable reagent pads in a pharmacy and complete the test at home. Follow all the instructions on the box or on the package insert. Do not skip steps and be sure to use a watch where timing is necessary.

Guaiac smear test samples are collected at home over a period of several days and analyzed in a laboratory. Containers for the stool will be provided by a doctor or technician. Collecting stool requires catching stool during a bowel movement and then placing it in specific containers. After placing it in the correct container, you may need to do one of the following:

• take it to the laboratory for analysis
• add a developing solution to the samples and wait for a colour change (this colour change will tell you if blood is present or absent)

How should I prepare for this test?

Testing for blood in the stool often requires three samples for analysis. To prepare for the test, you need to eat certain foods that are high in fibre and will cause you to have more frequent bowel movements. Consider eating these foods to increase your fibre:

• whole grain breads and cereals (e.g., bran cereal)
• corn or popcorn
• spinach
• prunes
• peanuts

Avoid the following for two to three days before the test because they may affect the test results:

anticoagulant (blood-thinning) medications (e.g., warfarin) ASA iron supplements nonsteroidal anti-inflammatory medications (NSAIDs) vitamin C tablets apples artichokes bananas bean sprouts beets broccoli

cabbage cantaloupe carrots cauliflower cucumbers grapefruit grapes horseradish mushrooms oranges potatoes radishes red meat turnips

Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications that you are taking. Also tell them about any medication allergies and medical conditions that you may have.

Ask your doctor or pharmacist whether you need to stop taking any of your medications before the test.

What can I expect after the test?

Wash your hands thoroughly with soap and water after collecting the samples.

Results

For some tests, you will interpret the results at home according to the instructions on the box or package insert. Interpreting results requires looking for a change in colour. The reaction between the stool and a chemical solution added to the sample produces the colour change. For other tests, samples will be sent to the laboratory to be interpreted.

Positive results mean there is blood in your stool. A positive result often requires further investigation with other tests including a colonoscopy, a flexible sigmoidoscopy exam, or barium enema. Even if you have had a positive result from the stool test, keep in mind that it is quite common to lose a small amount of blood from the digestive system, and further testing often shows normal results. Nevertheless, it is important to do further tests as there is an increased risk of having a serious condition such as inflammatory bowel disease or colorectal cancer.