A Cologuard test is a non-invasive screening method designed to detect signs of colorectal cancer and precancerous growths in individuals at average risk. This at-home test analyzes a collected stool sample for specific biological markers associated with disease development in the colon. When a positive result occurs, it indicates that one or more of these markers were detected, prompting the user to seek further diagnostic evaluation. A common concern for people taking the test is whether a benign, non-cancerous condition like hemorrhoids could potentially influence the outcome. The presence of conditions that cause bleeding can indeed trigger a positive result, which requires a deeper understanding of how the screening test functions.
How the Screening Test Detects Abnormalities
The Cologuard test employs a multi-target approach, analyzing the stool sample for two distinct types of biological indicators: altered DNA and the presence of blood. The DNA component searches for specific genetic mutations and epigenetic changes frequently shed by cancerous or precancerous cells into the stool. It targets seven specific point mutations in the KRAS gene, along with abnormal methylation markers for the NDRG4 and BMP3 genes, which are associated with colorectal neoplasia. The test uses advanced laboratory technology to amplify and quantify these trace amounts of human DNA, allowing for the detection of molecular changes.
The second component tests for human hemoglobin, a protein found in red blood cells. The presence of hemoglobin in the stool indicates bleeding somewhere in the lower gastrointestinal tract. This part of the test is highly sensitive and is similar to a Fecal Immunochemical Test (FIT), but it is combined with the DNA analysis to increase overall test accuracy. A sophisticated mathematical algorithm then combines the quantitative results from all the DNA alterations and the blood detection to generate a single positive or negative result.
The Connection Between Hemorrhoids and Test Results
Hemorrhoids are swollen veins in the rectum or anus and are a common source of non-malignant bleeding in the lower digestive tract. Because the Cologuard test detects human hemoglobin in the stool, active bleeding from internal or external hemorrhoids can directly lead to a positive screening result. The test is highly sensitive to the presence of blood but is unable to distinguish its source. It cannot tell the difference between blood shed by a cancerous lesion higher up in the colon and blood originating from a hemorrhoid at the anal opening.
Bleeding from this benign condition is why hemorrhoids can cause a positive outcome. The DNA portion of the test, which looks for specific cancer-related gene mutations, is not affected by the hemorrhoid itself. If a test is positive solely due to hemorrhoidal bleeding, the result is considered a “false positive” in the context of colorectal cancer screening. However, the test accurately reports the presence of blood, a finding that warrants investigation regardless of the suspected cause.
Test instructions often advise people not to collect a sample if they are experiencing active rectal bleeding, including bleeding known to be from hemorrhoids. If a test is collected during a period of active hemorrhoidal bleeding, the heightened sensitivity of the hemoglobin detection component increases the likelihood of a positive result.
Interpreting a Positive Result and Next Steps
A positive Cologuard result should never be interpreted as a definitive diagnosis of cancer. The next step following any positive result, regardless of whether hemorrhoids are suspected as the cause, is a diagnostic colonoscopy. It is important not to assume that the positive result was “just the hemorrhoids” and delay the necessary diagnostic procedure.
A colonoscopy is the definitive follow-up because it allows a gastroenterologist to visually examine the entire colon and rectum. This procedure can identify the exact source of any bleeding, whether it is from benign hemorrhoids, precancerous polyps, or a cancerous tumor. Any abnormal growths, such as polyps, can be immediately removed during the procedure, making the colonoscopy both a diagnostic and a therapeutic tool.
Medical guidelines recommend that a diagnostic colonoscopy be performed promptly after a positive screening result, ideally within three months and no later than six months. Delaying this follow-up significantly increases the risk of finding cancer at a more advanced stage. Discussing any existing conditions like hemorrhoids with a healthcare provider before the screening test is advisable, but a positive result still dictates the need for the gold-standard diagnostic procedure.