Overview

The stool DNA test is a noninvasive laboratory test that identifies DNA changes in the cells of a stool sample. The stool DNA test is a new method to screen for colon cancer.

The stool DNA test looks for abnormal DNA associated with colon cancer or colon polyps. The test also detects hidden blood in the stool, which can indicate the presence of cancer.

If a stool DNA test detects abnormal DNA, additional testing may be used to investigate the cause, such as a colonoscopy to examine the inside of the colon.

One stool DNA test (Cologuard) is approved for colon cancer screening in the United States.

Why it's done

Stool DNA testing is intended to screen for colon cancer or precancerous polyps in people with no symptoms.

The stool DNA test detects abnormal DNA and small amounts of blood shed into the stool from colon cancer or colon polyps.

When cancer or polyps are present in your colon, they continuously shed cells with abnormal DNA changes into the stool. The DNA changes are found in very tiny amounts, so very sensitive laboratory methods are required to detect them.

Research shows the stool DNA test is effective at detecting colon cancer and precancerous polyps. A positive test result usually requires a colonoscopy to examine the inside of your colon for polyps and cancer.

Risks

The stool DNA test is safe and poses no risks.

How you prepare

Stool DNA testing requires no preparation. You can eat and drink normally before the test and continue your current medications. There's also no need to undergo bowel preparation to clean out or empty your colon before the test.

What you can expect

During a stool DNA test you collect a stool sample and submit it to your doctor's office or mail it to a designated laboratory.

You'll receive a stool DNA test kit for collecting and submitting the stool sample. The kit includes a container that attaches to the toilet and a preservative solution that you add to the stool sample before sealing the container. The stool DNA test requires only one stool sample.

After the stool sample is collected, it can be returned to the doctor's office or sent by mail to the laboratory.

Results

Stool DNA test results may include:

  • Negative result. A test is considered negative if abnormal DNA changes common to colon cancer or precancerous polyps and signs of blood aren't found in the stool. Your doctor may recommend you repeat the test in three years.

  • Positive result. A test is considered positive if abnormal DNA changes common to colon cancer or precancerous polyps or signs of blood are found in the stool sample.

    Your doctor may recommend additional testing — typically a colonoscopy to examine the inside of the colon to determine if cancer or polyps are present.

    For every 20 people who undergo stool DNA testing, one or two will have a positive result, but no cancer or polyps will be found during a follow-up colonoscopy. In these instances, further testing is usually not recommended.