RisksBy Mayo Clinic Staff
Risks and limitations of the fecal occult blood test include:
June 06, 2014
The test isn't always accurate. Your fecal occult blood test could show a negative test result when cancer is present (false-negative result) if your cancer or polyps don't bleed.
Your test could show a positive result when you have no cancer (false-positive result) if you have bleeding from other sources, such as a stomach ulcer, hemorrhoid, or even blood swallowed from your mouth or your nose.
- Having a fecal occult blood test may lead to additional testing. When the fecal occult blood test result is positive but a follow-up colonoscopy is normal, your doctor may recommend further observation with another fecal occult blood test, evaluation of your upper gastrointestinal tract, a repeat colonoscopy or a combination of these.
- Fecal occult blood tests can't detect all cancers. Some cancers detected by colonoscopy may not be detected by the fecal occult blood test.
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