Cologuard is a non-invasive screening test that analyzes a stool sample for specific DNA markers and blood. These markers can indicate the presence of colorectal cancer or precancerous growths. Understanding a positive Cologuard result and the subsequent actions is important for effective colorectal cancer screening.
Interpreting a Positive Result
A positive Cologuard result does not indicate a cancer diagnosis. It means the test detected certain DNA markers or hemoglobin (blood) in the stool associated with colorectal cancer or advanced precancerous polyps. These markers can also be present for reasons other than cancer, such as non-cancerous polyps or other gastrointestinal conditions.
Cologuard works by analyzing stool for specific biomarkers, including altered DNA and hemoglobin. While Cologuard is highly sensitive for detecting colorectal cancer, identifying about 92% of cancers, its sensitivity for detecting large precancerous polyps is lower, around 42%. False positive results can occur, meaning the test is positive even when no cancer or advanced polyps are present, with a reported false-positive rate of approximately 13%.
The Essential Next Step: Colonoscopy
Following a positive Cologuard test, the next necessary step is to undergo a diagnostic colonoscopy. A colonoscopy is considered the most comprehensive method for colorectal cancer screening and prevention. It allows a gastroenterologist to directly visualize the entire lining of the colon and rectum. This direct examination is important for investigating the source of the markers detected by Cologuard.
During a colonoscopy, a long, flexible tube with a camera, called a colonoscope, is inserted into the rectum and advanced through the colon. Patients typically receive sedation to ensure comfort throughout the procedure, which usually takes about 30 to 60 minutes. The preparation for a colonoscopy involves a bowel cleanse to ensure a clear view of the colon lining. If any suspicious areas or polyps are identified during the procedure, the doctor can remove them immediately or take tissue samples for further analysis.
Potential Colonoscopy Findings
A diagnostic colonoscopy following a positive Cologuard result can reveal various findings. One common outcome is the detection of polyps, which are growths on the inner lining of the colon. Polyps can be benign (non-cancerous) or precancerous. Precancerous polyps, particularly adenomas, have the potential to develop into cancer over time if not removed. The colonoscopy allows for the removal of these polyps, preventing potential cancer development.
In some instances, the colonoscopy may detect colorectal cancer. If cancer is found, further staging and treatment planning will follow. It is also possible for the colonoscopy to find no significant abnormalities, even after a positive Cologuard test. This reinforces that a positive Cologuard result is a screening indicator and not a definitive diagnosis of cancer, and false positives do occur.
The Importance of Adherence
Adherence to the recommended colonoscopy after a positive Cologuard result is important. Delaying or avoiding this follow-up procedure can compromise the effectiveness of the initial screening and may lead to missed opportunities for early detection and intervention. Studies indicate that delaying colonoscopy beyond a few months after a positive stool test is associated with a higher risk of colorectal cancer.
Colorectal cancer is often treatable when identified early. The prompt completion of a diagnostic colonoscopy allows for the timely removal of precancerous polyps or the early diagnosis of cancer, which significantly improves treatment outcomes. Most insurance plans, including Medicare, cover the cost of a follow-up colonoscopy after a positive non-invasive stool-based test, recognizing its role as a continuation of the screening process.