Cologuard; Colon cancer screening - Cologuard; Stool DNA test - Cologuard; FIT-DNA stool test; Colon precancer screening - Cologuard
Cologuard is a screening test for colon and rectal cancer.
The colon sheds cells from its lining every day. These cells pass with the stool through the colon. Colon cancer cells may have DNA changes in certain genes. Cologuard detects the altered DNA. The presence of abnormal cells or blood in the stool may indicate cancer or precancer tumors.
Colon cancer may not be talked about as often as other cancers, like breast cancer, prostate or lung cancer, but it's actually one of the leading causes of cancer deaths. It is for this reason it's very important to stay on top of your colon health. The colon is your large intestine, the long, upside-down U-shaped tube that is toward the end of the line for getting rid of waste in your body. Colon cancer can start in the lining of the intestine, or at the end of it, called the rectum. Let's try to better understand Colon cancer. You're more likely to get the disease if you're over age 60, especially if you have a family history of colon cancer, inflammatory bowel disease, diabetes, or obesity. Smoking cigarettes and drinking alcohol has also been found to increase your risk of getting colon cancer. Although the data are not consistent, eating red meat or processed meats may increase the risks of colon cancer as well. Lean, unprocessed red meat, may be associated with less risk. If you have symptoms, they may include pain in your abdomen, blood in your stool, weight loss, or diarrhea. But hopefully, you'll get diagnosed before you have any symptoms, during a regular screening test like a colonoscopy or sigmoidoscopy. These tests use special instruments to see inside your colon and rectum to look for any cancerous or pre-cancerous growths, called polyps. If your doctor discovers that you do have colon cancer, unfortunately, you'll need to have a few more tests, including scans of your abdomen to find out whether the cancer has spread, and if so, where in your body it's located. So, how is colon cancer treated? That really depends on how aggressive your cancer is and how far it's spread, but usually colon cancer is removed with surgery, or killed with chemotherapy or radiation. You may get one, or a combination, of these treatments. Colon cancer is one of the more treatable cancers. You can be cured, especially if you catch it early. Spotting colon cancer when it's still treatable is up to you. If you're over age 45, you need to get screened. And, regular physical activity and eating at least some fruits and vegetables daily, perhaps with unprocessed wheat bran, can help prevent it. If you want to prevent colon cancer, you'll also want to avoid processed and charred red meats, and smoking, and excess calories, and alcohol.
How the Test is Performed
The Cologuard testing kit for colon and rectal cancer must be ordered by your health care provider. It will be sent by mail to your address. You collect the sample at home and send it back to the lab for testing.
The Cologuard testing kit will contain a sample container, a tube, preserving liquid, labels, and instructions on how to collect the sample. When you are ready to have a bowel movement, use the Cologuard testing kit to collect your stool sample.
Read the instructions that come with the testing kit carefully. Wait until you are ready to have a bowel movement. Collect the sample only when it is possible to ship it within 24 hours. The sample must reach the lab in 72 hours (3 days).
DO NOT collect the sample if:
Follow these steps to collect the sample:
- Read all instructions that come with the kit.
- Use the brackets provided with the testing kit to fix the sample container on your toilet seat.
- Use the toilet as usual for your bowel movement.
- Try not to let urine get into the sample container.
- Do not put toilet paper into the sample container.
- Once your bowel movement is over, remove the sample container from the brackets and keep it on a flat surface.
- Follow instructions to collect a little sample in the tube provided with the testing kit.
- Pour the preserving liquid in the sample container and close the lid tightly.
- Label the tubes and the sample container according to the instructions, and place them in the box.
- Store the box at room temperature, away from direct sunlight and heat.
- Ship the box within 24 hours to the lab using the label provided.
The results of the test will be sent to your provider in two weeks.
Colon cancer is one of the leading causes of cancer-related deaths in the United States. The good news is that earlier diagnosis due to screening tests often leads to a complete cure. Colorectal cancer starts in the large intestine, also known as the colon. Nearly all colon cancers begin as noncancerous, or benign, polyps, some of which may slowly develop into cancer. Screening can detect these polyps and early cancers. Polyps can be removed years before cancer even has a chance to develop. Your doctor can use two types of tools to screen for cancer. The first type is a stool test. Polyps in the colon and small cancers can bleed tiny amounts of blood that you can't see with the naked eye. The most common method to test for the presence of blood is the fecal occult blood test or FOBT. This test checks your stool for small amounts of blood that you may not be able to see. Two other stool tests are the fecal immunochemical test and the stool DNA test. The second type of screening tests involve looking at the lining of the colon. One of these tests is a sigmoidoscopy exam. This test uses a flexible scope to look at the lower portion of your colon. But, because it looks only at the last one-third of the large intestine, it may miss some cancers. So this test is done along with a stool test. A colonoscopy is similar to sigmoidoscopy, but it can see the entire colon. For this test, your doctor will give you instructions for cleansing your bowel. This is called bowel preparation. During the colonoscopy, you’ll receive medicine to make you relaxed and sleepy. Another test your doctor may recommend is a virtual colonoscopy, also called a CT colonography. This test uses a CAT scan and computer software to create a 3-D image of your large intestine. Beginning at age 45, all men and women should have a screening test for colon cancer. Screening options for people with average risk for colon cancer include visual based exams. These could be a colonoscopy every 10 years starting at age 45 or a virtual colonoscopy every 5 years. A Flexible sigmoidoscopy every 5 years or a Flexible sigmoidoscopy every 10 years plus stool testing with FIT done every year. Screening options also include stool based tests. People with average risk should have an FOBT or FIT every year. A colonoscopy is needed if the results are positive, or a Stool DNA test every 1 to 3 years. A colonoscopy is needed if the results are positive. People with certain risk factors for colon cancer may need screening at a younger age, or they may need screening more often. Such people include those with a family history of colon cancer, those with a history of previous colon cancer or polyps, or people with a history of ulcerative colitis or Crohn disease. The death rate for colon cancer has dropped in the past 15 years and this may be due to increased awareness and colon screening. In general, early diagnosis is much more likely to lead to a complete cure.
How to Prepare for the Test
The Cologuard test does not require any preparation. You do not need to change your diet or medicines before the test.
How the Test will Feel
The test requires you to have a normal bowel movement. It will not feel any different from your regular bowel movements. You can collect the sample at your home privately.
Why the Test is Performed
The test is done to screen for colon and rectal cancer and abnormal growths (polyps) in the colon or rectum.
Your provider may suggest Cologuard testing once every 1 to 3 years starting at age 45 years. The test is recommended if you are age 45 to 75 years and have an average risk of colon cancer. This means that you do not have:
The normal result (negative result) will indicate that:
- The test did not detect blood cells or altered DNA in your stool.
- You do not need further testing for colon cancer if you have an average risk of colon or rectal cancer.
What Abnormal Results Mean
Abnormal result (positive result) suggests that the test found some pre-cancer or cancer cells in your stool sample. However, the Cologuard test does not diagnose cancer. You will need further tests to make a diagnosis of cancer. Your provider will likely suggest a colonoscopy.
There is no risk involved in taking the sample for Cologuard test.
Screening tests carry a small risk of:
- False-positives (your test results are abnormal, but you do NOT have colon cancer or pre-malignant polyps)
- False-negatives (your test is normal, even when you have colon cancer)
It is unclear yet whether the use of Cologuard will lead to better outcomes compared with other methods used to screen for colon and rectal cancer.
Bresalier RS. Colorectal cancer. In: Feldman M, Friedman LS, Brandt LJ, eds. Sleisenger and Fordtran's Gastrointestinal and Liver Disease. 11th ed. Philadelphia, PA: Elsevier; 2021:chap 127.
Eckmann JD, Ebner DW, Bering J, et al, eds. Multitarget stool DNA screening in clinical practice: high positive predictive value for colorectal neoplasia regardless of exposure to previous colonoscopy. Am J Gastroenterol. 2020;115(4):608-615. PMID: 32068535.
NCCN clinical practice guidelines in oncology (NCCN Guidelines) colon cancer, version 2.2023.
US Preventive Services Task Force, Davidson KW, Barry MJ, et al. Screening for Colorectal Cancer: US Preventive Services Task Force Recommendation Statement. JAMA. 2021;325(19):1965-1977. PMID: 34003218
Last reviewed on: 5/3/2023
Reviewed by: Michael M. Phillips, MD, Emeritus Professor of Medicine, The George Washington University School of Medicine, Washington, DC. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.