Another examination in colorectal cancer screening is the occult blood test. The test can be used to detect even small traces – invisible to the eye – of hidden (occult) blood in the stool. Blood in the stool can be an indication of polyps or tumors. The test can be obtained from a family doctor. Alternatively, one of the newer immunological occult blood tests can be purchased at the pharmacy and sent to a laboratory for evaluation or can be evaluated at home by the patient. Public health insurers pay for the older chemical occult blood test at the family doctor’s office from the age of 50.
Stool tests: regular performance important
Stool tests absolutely must be repeated annually, and any positive result must be clarified by colonoscopy. Because polyps and tumors do not bleed continuously but at uncertain intervals, stool tests can find only about 30 percent (detection rates are higher for immunologic stool tests) of polyps or tumors. The test result of chemical occult blood tests can also be falsified by certain foods.
A stool test in common use since 2002 is the tumor M2-PK test, which detects a tumor-specific enzyme in the stool instead of blood and in this way detects any intestinal tumors that may be present. This test is available from doctors or pharmacies. Scientific long-term studies on this test are not yet available.
Palpation examination of the rectum
Another method used as part of annual cancer screening is palpation of the rectum, in which the physician feels the rectum with a finger to detect changes in the mucosa. However, this method alone is insufficient for colorectal cancer screening because only tumors in the lower rectum can be detected and all the rest of the rectum and colon are not examined at all. Only one-third of tumors grow in the rectum and more often colorectal cancer develops in the upper part of the colon.
Blood testing by Septin 9 test
A new form of early colorectal cancer detection is offered by the Septin 9 blood test. If a colorectal tumor is present, altered genetic material is released into the blood at an early stage, which can be detected by the Septin 9 blood test. Depending on the stage, the detection rate with this method is at least 67%, which is higher than that of stool blood tests but lower than that of colonoscopy.
Septin 9 blood testing does not require prior diet or bowel evacuation, thus requiring little time. It can also be used in patients for whom colonoscopy is not feasible. The Septin 9 blood test is not covered by health insurance and is not yet offered by every practice, nor are there currently (February 2011) any longer-term studies available on it.
