The stool guaiac test finds hidden (occult) blood in the stool (bowel movement), even when you cannot see the blood yourself.
It is the most common form of fecal occult blood test (FOBT) in use today.
Guaiac smear test; Fecal occult blood test - guaiac smear; Stool occult blood test - guaiac smear
How the test is performed
In the most common way of doing a stool guaiac test, a small sample of stool is placed on a paper card and a drop or two of testing solution is added. A color change is a sign of blood in the stool.
If the test is performed in an office or hospital, a doctor may collect a small amount of stool during a rectal examination.
If the test is performed at home:
- You will need to collect a stool sample from three bowel movements, one right after the other.
- You will then smear a small amount of stool on a card, and mail it to a laboratory for testing.
There are many ways to collect the samples:
- You can catch the stool on plastic wrap that is loosely placed over the toilet bowl and held in place by the toilet seat. Then put the sample in a clean container.
- Some test kits supply a special toilet tissue that you use to collect the sample, then put the sample in a clean container.
Do not take stool samples from the toilet bowl water, because this can cause errors.
Review Date: 11/12/2010
Reviewed By: Todd Eisner, MD, Private practice specializing in Gastroenterology, Boca Raton, FL. Clinical Instructor, Florida Atlantic University School of Medicine. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.