The fecal occult blood test for colorectal cancer may be your next best option to a colonoscopy.
For people age 50 and older, health organizations such as the American Cancer Society and the American College of Gastroenterology recommend regular screening for colorectal cancer—preferably a colonoscopy every 5–10 years. That’s all well and good, but only 25% of people follow these recommendations, perhaps because they think the tests will be painful or embarrassing or will not be covered by insurance. Actually, Medicare and most private health insurance plans pay for colorectal cancer tests.
Researchers are working on less invasive tests for colorectal cancer, such as virtual colonoscopy. But one of the easiest ways to comply with the colorectal cancer screening recommendations is to do an annual fecal occult blood test in the privacy of your own home (although you should still consider having a colonoscopy every 5–10 years).
This simple, low-risk test checks for minute amounts of blood in your stool, the presence of which can signal colorectal cancer. While not the best colorectal cancer screening option, a fecal occult blood test can detect colorectal cancer in 30–50% of people who have colorectal cancer, and annual testing can reduce the risk of death from colorectal cancer by up to 33%.
Where to get a fecal occult blood test for colorectal cancer
You can get a fecal occult blood test from your doctor, or you can buy one from a pharmacy or online. There are two types of fecal occult blood tests: the traditional, guaiac-based tests and the newer, fecal immunochemical tests.
Doctors typically give their patients a traditional, guaiac-based fecal occult blood test (such as Hemoccult, Seracult, or Coloscreen), along with instructions on how to perform the test at home. You’ll probably be asked to take stool samples from bowel movements on three separate days; cancers and other disorders typically produce bleeding only intermittently. Most tests require that you collect the stool in a container before it drops into the toilet bowl, and then use an applicator stick to smear a small amount of the stool on a special card. Depending on the test you receive, you may be instructed either to apply the chemical guaiac to the card to see if the stool turns blue (which indicates that blood has been detected) or to return the sample to your doctor’s office or a laboratory for analysis.
Some doctors give the newer, fecal immunochemical tests (such as InSure FIT). These tests analyze your stool sample for the presence of hemoglobin, a component of blood. The test requires that after you have a bowel movement you brush the surface of the stool in the toilet bowl with a specially provided brush. You then dab the brush onto a test card, and, after taking a second sample from another bowel movement on a different day, you mail the card to a laboratory for analysis.
You can buy a fecal occult blood test—both the traditional and the newer kinds—at your local pharmacy or online, but we recommend that you don’t do this. These tests may appear to be easier to use, and you might like the idea of not having to make an appointment with your doctor, but using a fecal occult blood test given by your doctor and interpreted by your doctor will decrease the likelihood of missing a colorectal cancer or wrongfully deciding that you have colorectal cancer. With the self-bought tests, you’re on your own and thus more likely to perform the test incorrectly or misinterpret the results.
When the results are positive for colorectal cancer
If your fecal occult blood test is positive for colorectal cancer, your doctor will likely want to perform a colonoscopy to find the source of the bleeding. Colorectal cancer isn’t the only possible cause of blood in the stool. Precancerous polyps in the colon and rectum can also produce bleeding; removing these polyps can reduce the risk of colorectal cancer in the future. Blood in the stool can also be a sign of hemorrhoids, anal fissures, diverticular disease (diverticulosis or diverticulitis), a peptic ulcer, or inflammatory bowel disease (Crohn’s disease or ulcerative colitis).
Because so many people are not having a colonoscopy to screen for colorectal cancer, researchers are attempting to improve the accuracy of the fecal test. In one study, a newly developed stool DNA test called PreGen-26, which looks for genetic defects that signal cancer, was compared to the traditional guaiac-based test, and found to be superior: It detected half of colorectal cancers (which were definitively diagnosed via colonoscopy), while the traditional test only found 13% of colorectal cancers (this was an unusually low detection rate, compared with the results of other studies).
The DNA test also uncovered 18% of colon polyps, vs. the 11% found by the usual fecal test. The DNA test differs slightly from the fecal occult blood test in that an entire bowel movement needs to be collected for mailing or delivery to a laboratory. Some people may find this to be an unpleasant task. Although the DNA test is now available, it is difficult to get, is expensive (it costs between $400 and $800 compared with the $3–47 charged for a traditional fecal test), and the bowel movement must be sent to a special laboratory. In general, gastroenterologists at Johns Hopkins are not giving this test to their patients, because there is not yet enough evidence that the improved colorectal cancer detection rate is worth the expense and trouble of the test.
Our advice on colorectal cancer screening tests
We encourage you to follow the recommendations of the American Cancer Society and the American College of Gastroenterology and have a yearly fecal test (either the traditional, guaiac-based test or the immunochemical test). Even better, combine your yearly fecal occult blood test with a colonoscopy every 5–10 years. A colonoscopy is nothing to fear. You’ll be sedated during the test and will most likely not feel or remember a thing. In fact, people who undergo a colonoscopy typically complain about the “prep,” which involves following a clear liquid diet for a day or two and taking laxatives to clean the bowels, rather than the procedure itself.
