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Results
By Mayo Clinic staffYour doctor will review the results of your stool DNA test and then share the results with you.
- Negative result. A test is considered negative if DNA markers common to colon cancer or precancerous polyps are not found in your stool.
- Positive result. A test is considered positive if DNA markers common to colon cancer or precancerous polyps are found in your stool sample. Additional evaluation - such as colonoscopy — might be recommended to determine whether you have cancerous or precancerous changes in your colon or other parts of your digestive system.
- False-negative result. A false-negative result — a negative test result when cancer is present — may occur if colon cancer or polyps do not harbor DNA markers targeted by the stool DNA test, or if markers are present in extremely low amounts. While next-generation stool DNA test methods appear to be capable of detecting most colon cancers and precancerous polyps, further study is needed to determine what the rate of false-negative results will be.
- False-positive result. A false-positive result — a positive test for cancer when no cancer is present — may occur in about 5 to 10 percent of people screened. False-positives could be due to the presence of tumors above the colon or to a problem with the test. When the stool DNA test result is positive but a follow-up colonoscopy is normal, your doctor may recommend further observation with another stool DNA test, evaluation of your upper gastrointestinal tract, a repeat colonoscopy or a combination of these. Research is being done to clarify the best way to manage false-positive results.
References
- Fletcher RH. Screening strategies in patients at average risk for colorectal cancer. http://www.uptodate.com/home/index.html. Accessed March 13, 2009.
- Levin B, et al. Screening and surveillance for the early detection of colorectal cancer and adenomatous polyps, 2008: A joint guideline from the American Cancer Society, the US Multi-Society Task Force on Colorectal Cancer, and the American College of Radiology. Gastroenterology. 2008;134:1570.
- Screening for colorectal cancer: U.S. Preventive Services Task Force recommendation statement. Annals of Internal Medicine. 2008;149:62.
- Ahlquist DA. Next generation stool DNA testing: Expanding the scope. Gastroenterology. 2009;136:2068.
- Ahlquist DA, et al. Stool DNA and occult blood testing for screen detection of colorectal neoplasia. Annals of Internal Medicine. 2008;149:441.
- Itzkowitz S, et al. A simplified, noninvasive stool DNA test for colorectal cancer detection. American Journal of Gastroenterology. 2008;103:2862.
- Zou H, et al. High detection rates of colorectal neoplasia by stool DNA testing with a novel digital melt curve assay. Gastroenterology. 2009;136:459.
