5 Things You Need to Know About Colorectal Home Test Kits
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Colorectal cancer is a disease that affects both men and women, and usually begins to advance from one’s 40s. The onset can be much earlier depending on the risk factors present, and for those who exhibit the associated signs and symptoms, a screening or diagnostic colonoscopy is in order.
While colonoscopy is considered the benchmark for accurate testing for colorectal cancer, such comprehensive tests can cause discomfort to patients both physically and mentally. These tests are also costly and are not prescribed to everyone; those who are of average risk are instead directed to screening test alternatives, many of which are at-home stool-based tests.
A fecal occult blood test.
Source: Steve Horrell/Science Photo Library.
If your risk of colorectal cancer is average and the doctor has recommended periodic screening, here are five things you should know before you begin.
1. Home test kits are recommended for those who do not have symptoms of colorectal cancer.
First of all, if you are experiencing any symptoms of colorectal cancer such as prolonged changes in your bowel movement, blood in the stool and abdominal pain, put that home test kit down and speak to your doctor instead.
The goal of at-home colorectal cancer test kits is to detect the presence of colorectal cancer as early as possible while the symptoms are not present. Having a tube inserted into your body is uncomfortable, not to mention highly unappealing, and home-based test kits do not require such procedures so as to encourage more people who are at average risk to regularly monitor their colorectal health.
2. The tests are non-invasive and can be done in the privacy of your own home.
`A key difference between home test kits and those conducted at the hospital is the non-invasive nature of home-based tests.
More comprehensive tests like colonoscopies require the insertion of a tube through the anus and also pumping air into the colon to ensure that the intestinal lumen can be well-visualized. This can cause not only discomfort but can also result in mechanical trauma to the intestinal lining, which can cause small bleeding to happen for a few days after the test.
An ongoing colonoscopy. Source: Dr P. Marazzi/Science Photo Library.
It also has to be conducted at a hospital, and especially for first-timers, exposing an intimate part of yourself may be nerve-wracking and anxiety-inducing, even if it’s to medical professionals and for health purposes.
Home-based tests, on the flip side, are completely non-invasive and can be conducted in the privacy of your own home without doctors’ supervision; though, collecting stool samples may still be an uncomfortable and awkward experience for first-timers.
3. The tests need to be done more frequently than others.
Many stool-based tests detect the presence of occult or hidden blood in the stool, which typically originates from larger polyps on the intestinal lining. These polyps have more fragile blood vessels that may rupture when agitated by digested food matter passing through the large intestine and rectum.
However, colorectal polyps can take a long time to grow, sometimes taking 10 to 15 years before they become cancerous. As a result, these fecal occult blood tests, or FOBTs, do not detect polyps as well as colonoscopies do. More often than not, smaller polyps may not bleed at the time of the screening, which is why most stool-based tests are typically done yearly.
On the other hand, fecal immunochemical (FIT) -DNA tests, which test for both occult blood and abnormal DNA resulting from mutations that cause cancerous growth, are more sensitive and need only be done every three years.
4. You may have to watch your food/drug intake prior to the test.
This is different from preparing for a colonoscopy, which requires that bowels are cleared before the procedure, either through the use of laxatives, fasting, or consuming a liquid diet in the days leading up to the colonoscopy.
Examples of NSAIDs include ibuprofen and aspirin, which should be avoided before a stool test. Acetaminophen, an alternative name for paracetamol, is not an NSAID and can still be taken.
Source: Sherry Yates Young/Science Photo Library.
A dietary restriction where NSAIDs (non-steroidal anti-inflammatory drugs), red meat and food high in iron, and a vitamin C intake exceeding 250mg a day should be avoided applies to the guaiac-based FOBT (gFOBT), which uses the chemical called guaiac to detect the presence of blood in the stool. The restriction helps ensure that any blood found is a result of bleeding in the intestine or rectum, rather than diet.
5. Beware the false positives and negatives.
You’ve heard of pregnancy scares, where a pregnancy test gives a positive result, but further checks reveal that it’s a false alarm as a result of other factors.
Particularly for FOBTs and FITs that are good indicators and generally reliable tests for fecal occult blood, accuracy is not 100% and can still produce false results for colorectal cancer.
False positive results happen when blood is found in the sample, but subsequent investigation through a colonoscopy does not reveal the presence of any polyps. Conditions such as hemorrhoids, or even contamination by menstrual blood when collecting stool samples can result in false positives, and the test is not sophisticated enough to distinguish between blood from different origins.
Colon cancer screening test kit card with test results. The fecal samples on a guaiac-impregnated filter paper have been treated with hydrogen peroxide in the laboratory and one sample has reacted positively (blue color) indicating the likely presence of blood and the need for further tests.
Source: James King-Holmes/Science Photo Library.
False negative results may also arise as a result of bleeding not being present at the time of screening, usually due to polyps still being too small.
Particularly for false positive results, these may cause unnecessary anxiety, especially if it turns out to be a false alarm. Nonetheless, assumptions about the results should not be made and should be followed with a doctor’s consultation to further investigate the potential cause.
False negatives present a different kind of danger, as they can present an inaccurate outlook that you’re in perfect health. Such assumptions can result in testing less frequently, and is associated with increased mortality when cancer detection becomes delayed. For this reason, the recommended interval between screenings is one year for fecal occult blood tests.
