Fecal Occult Blood Testing (Hemoccult)
The fecal occult blood test is a stool (fecal)
examination to test for the presence of minute (occult) amounts of blood that
can't be seen. The test consists of a 3 X 3 inch card with two small windows
covered with a special impregnated paper. Your doctor may smear a small amount
of stool on the windows after she does a rectal examination or she may ask you
to place 2 smears from each of 3 consecutive stools on 3 cards by yourself in
the privacy of your home. Only a small quantity of stool on each window is
required. The slides are "developed" by applying a few drops of a hydrogen
peroxide solution. Any blue color indicates a positive test.
The fecal occult blood test (FOBT) was developed as a screening test for
colorectal cancer. We know that a positive FOBT in a patient over 50 has about a
1 in 10 to 1 in 6 chance of demonstrating the presence of a colon cancer and
about the same chance of revealing a colon polyp that may eventually develop
into cancer. Based on the results of several large clinical studies, patients
who have polyps or cancers detected by FOBT have 25 to 35% better survival than
people in the same age group who do not have their stools tested. The National
Cancer Institute, The American Cancer Society, and a variety of physician and
lay groups all counsel patients over age 50 to have an FOBT every year. As of
January 1, 1998 the Federal Government will reimburse physicians who prescribe
FOBT for patients who have Medicare coverage.
Several medications, including aspirin, coumadin, arthritis medications (except
acetaminophen {Tylenol}), as well as red meat, horseradish, and rhubarb can
cause "false positive" tests. That is, they may show a positive blue color on a
stool smear when there is no bleeding from the colon. Patients should make every
effort to follow the package directions before doing FOBT. Patients who can see
blood in their stool don't need an FOBT to confirm the bleeding, they need an
investigation of the gut to find a source for the bleeding.
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