Home > Health & Wellness > Health Library > Stool Tests for Colorectal Cancer
A stool test is one of many tests used to look for colorectal cancer. These tests may find cancer early, when treatment works better. Colorectal cancer affects the large
intestine (colon) and the
The most common stool tests include:
A newer stool test is the stool DNA (sDNA). This test is still being studied to see how well it works to find colorectal cancer.
Blood in the stool may be the only symptom of
colorectal cancer, but not all blood in the stool is caused by cancer. Other
conditions that can cause blood in the stool include:
A stool test is one of many tests that may be used to screen for colon cancer. Other tests include sigmoidoscopy, colonoscopy, and computed tomographic colonography. Which screening test you choose depends on your risk, your preference, and your doctor. Talk to your doctor about what puts you at risk and what test is best for you.
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Stool tests are done:
Since colorectal cancers do not bleed
all the time, most stool tests are done over several days on
different stool samples. This increases the chance of finding blood in
your stool if it exists.
You may need to avoid certain foods for 2 to 3 days before the test. This depends on what kind of stool test you use. If you aren't sure, ask your doctor.
Do not do the stool tests during your menstrual period or if you
have active bleeding from hemorrhoids. Also, do not test a stool sample that
has been in contact with toilet bowl cleaning products that turn the water
Talk to your doctor about any concerns you have
regarding the need for the test, its risks, how it will be done, or what the
results will mean. To help you understand the importance of this test, fill out
medical test information form(What is a PDF document?).
For a stool test, it may be helpful to catch the stool on some plastic wrap draped loosely over the toilet bowl and held in place by the toilet seat.
For tests that require more than one sample, be sure to collect each sample the same way.
The FIT may also be called the iFOBT.
Instructions are provided by the companies that make the test kits. Each kit is different. Your kit will include a list of steps for you to follow to get accurate results. The test kit may include brushes and test cards. And you may need to collect a stool sample on 2 or more days.
The FIT test doesn't require a special diet in the days before you take the test.
You will need to collect stool samples over three different bowel movements on three different days. The test kit includes a wooden applicator and test cards. Be sure to follow the instructions that come with your test kit, including any instructions to avoid certain foods in the days before the test.
Other ways to do FOBT:
If there is blood in your stool, call your doctor as soon as possible.
You may find it unpleasant to collect a
stool sample for these tests.
There is no risk from the stool test itself. For this test, you put a sample of stool on a card or you collect a stool sample.
But there are some important things to think about. If your test is positive, you will need to have a colonoscopy. This would be used to see if the stool test result is from colorectal cancer. But blood in the stool is more often caused by something other than cancer. These other causes could include hemorrhoids, ulcers, or taking aspirin. A positive test result could lead you to worry. And you might have a colonoscopy that you didn't need.
FIT test results are read by your doctor. The results of some FOBT kits can be read by you.
A normal FIT or FOBT test means that there was no blood in your stool at the time of the test.
Normal test results are called negative.
An abnormal FIT or FOBT test means that there was some blood in your stool at the time of the test. Abnormal test results are called positive.
If a stool test is normal, it does not always mean
colorectal cancer or
colon polyps are not present. That's because these tests can miss polyps and some cancers.
Talk with your
doctor about how often you should do a test, depending on your age
and any risk factors you may have for colorectal cancer.
A colon polyp, a precancerous polyp, or cancer
can cause a positive stool test. With a positive test, there is a small chance that
you have early-stage colorectal cancer.
Talk with your doctor about what test you may need next. Most of the time, an abnormal stool test means that you will need to have a colonoscopy.
Reasons you may not be able to
have a stool test or why the results may not be helpful include:
Other Works Consulted
Chernecky CC, Berger BJ (2013). Laboratory Tests and Diagnostic Procedures, 6th ed. St. Louis: Saunders.
Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.
Haas JS (2013). Adult preventive health care. In EG Nabel, ed., ACP Medicine, section 2, chap. 2. Hamilton, ON: BC Decker.
Hoffman RM, et al. (2010). Colorectal cancer screening adherence is higher with fecal immunochemical tests than guaiac-based fecal occult blood tests: A randomized, controlled trial. Preventive Medicine, 50(5–6): 297–299.
Levin B, et al. (2008). Screening and surveillance for the early detection of colorectal cancer and adenomatous polyps, 2008: A joint guideline from the American Cancer Society, the U.S. Multi-Society Task Force on Colorectal Cancer, and the American College of Radiology. CA: A Cancer Journal for Clinicians, 58(3): 130–160.
Pagana KD, Pagana TJ (2010). Mosby’s Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.
ByHealthwise StaffPrimary Medical ReviewerAdam Husney, MD - Family MedicineE. Gregory Thompson, MD - Internal MedicineSpecialist Medical ReviewerArvydas D. Vanagunas, MD - Gastroenterology
Current as ofMarch 18, 2016
Current as of:
March 18, 2016
Adam Husney, MD - Family Medicine & E. Gregory Thompson, MD - Internal Medicine & Arvydas D. Vanagunas, MD - Gastroenterology
To learn more about Healthwise, visit Healthwise.org.
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