Skip to content
My WebMD Sign In, Sign Up

Colorectal Cancer Health Center

Font Size

Stool Tests for Colorectal Cancer

Results

For some FOBT kits, you can read the results yourself. Other tests, including FIT/iFOBT and stool DNA, are read by your doctor.

Stool tests
Normal:

A normal FIT/iFOBT or FOBT test means that there was no blood in your stool at the time of the test. A normal sDNA test means that no abnormal cells were found. Normal test results are called negative.

Abnormal:

An abnormal FIT/iFOBT or FOBT test means that there was some blood in your stool at the time of the test. An abnormal sDNA test means that some abnormal cells were found. Abnormal test results are called positive.

Normal results

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.

Abnormal results

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.

What Affects the Test

Reasons you may not be able to have a stool test or why the results may not be helpful include:

  • Having blood in the urine, menstrual bleeding, hemorrhoids, an anal fissure, bleeding gums, or nosebleeds.
  • Having cleaning products in the toilet water at the time of the test.

What To Think About

  • Stool tests can produce false-positive and false-negative results.
    • False-positive means that the test may be positive when you don't have a polyp or cancer.
    • False-negative means that the test may be negative when you do have a polyp or cancer.
  • These tests may miss polyps and some cancers.
  • The stool DNA test is still new, and it isn't available everywhere.

Related Information

Other Works Consulted

  • Chernecky CC, Berger BJ (2008). Laboratory Tests and Diagnostic Procedures, 5th ed. St. Louis: Saunders.

  • Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.

  • Helfand M (2009). Adult preventive health care. In EG Nabel, ed., ACP Medicine, Clinical Essentials, chap. 10. 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.

  • Nadel MR, et al. (2005). A national survey of primary care physician's methods for screening for fecal occult blood. Annals of Internal Medicine, 142(2): 86–94.

  • Pagana KD, Pagana TJ (2010). Mosby’s Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.

WebMD Medical Reference from Healthwise

Last Updated: January 17, 2012
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

Today on WebMD

colorectal cancer slideshow
SLIDESHOW
what is your cancer risk
HEALTH CHECK
 
Colon Cancer Survival
VIDEO
Kemeny Chemo Side Effects
VIDEO
 

bread
ARTICLE
Colon vs Rectal Cancer
VIDEO
 
New Colorectal Treatments
VIDEO
can lack of sleep affect your immune system
FEATURE
 

Cancer Facts Quiz
QUIZ
Virtual Colonoscopy
VIDEO
 
Picture of the Colon
ANATOMY
Vitamin D
SLIDESHOW
 

WebMD Special Sections