Cologuard® or Colonoscopy?
Asheville Gastroenterology recommends colonoscopy as the best test to prevent colorectal cancer. Colonoscopy is the only test to screen, prevent, detect, treat, and cure significant colon lesions during one exam.
What is Cologuard®?
Cologuard® is a new, noninvasive colon cancer screening test that does not require any preparation or dietary changes. It can be used by men and women 50 years of age and older who are at average risk for colon cancer. It should not be used by those who are at higher risk for colon cancer including those with a history of inflammatory bowel disease or a known family history of colon cancer or precancerous polyps, or those with symptoms, such as visible blood in stool.
How does Cologuard® work?
If cancerous or precancerous tissue is in your colon, those abnormal cells may be picked up by stool as it passes through your colon. Cologuard® uses laboratory technology to find the DNA from these abnormal cells. Cologuard® is not a genetic test; it only looks for altered DNA associated with colon cancer and precancerous cells in the colon. It also looks for non-visible blood in stool.
How is the Cologuard® test performed?
The Cologuard® test is performed by collecting a stool sample at home with a kit that is provided by Cologuard®. This process involves placing a plastic collection bucket on the toilet seat, collecting the stool sample, scraping the sample with a collection probe and placing the remaining stool sample in a liquid solution. The stool sample needs to be shipped to a laboratory for evaluation within 3 days of collection. A physician will review the results of the study and will order additional tests as needed.
All positive Cologuard® results should be followed by a diagnostic colonoscopy. Following a negative result, patients should continue participating in a routine screening program. Guidelines have not been established for how frequently the Cologuard® test should be performed.
How does Cologuard® compare to other noninvasive tests?
The fecal immunochemical test, also known as “FIT,” is a noninvasive colorectal cancer screening test that has been around for many years. The FIT test is widely available and is included in all the U.S. colorectal cancer screening guidelines.
In clinical studies, Cologuard® found 92% of colon cancers and 42% of advanced precancerous tissue in the colon; in other words, it missed 8% of colon cancers and it missed almost 60% of the advanced precancerous tissue. It was more sensitive than the FIT test in detecting colorectal cancer. However, false positives and false negatives can occur with any test. Cologuard® was positive in 13% of people without cancer as compared to the FIT test with a 5% false positive rate.