Guaiac-based stool testing is a way to detect occult blood in the stool. The presence of blood in the stool suggests that a colon cancer might be present, and a follow-up colonoscopy may be needed. The test does not confirm the existence of colon cancer and there are many false positives and other sources of fecal blood besides colon cancer. Guaiac-based stool testing—even newer kinds—have low sensitivity, so they need to be administered more than once. The test is usually done three times spread out over time. Cologuard is a multiplex stool DNA test that detects DNA markers and also uses an immunochemical test to detect hemoglobin. This is not guaiac-based stool testing.