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Fecal Occult
Blood Test
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What is the
test?
This test detects blood in your stool, which
can be a sign of bleeding anywhere from your
nose and mouth to your rectum, such as from an
ulcer, a polyp, or cancer. If you're over 50,
you should have this test annually during the
years when you don't have either a colonoscopy
or sigmoidoscopy to screen for colon cancer.
Keep in mind, however, that both colonoscopy
and sigmoidoscopy are better at detecting cancer
than a fecal occult blood test.
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How
do I prepare for the test?
If the traditional test is used, you collect
samples of your stool at home and send them to
a laboratory or clinic for analysis.Your doctor
gives you a kit with all of the materials you
need.A newer test uses flushable pads to detect
blood in the toilet bowl following a bowel movement,
so that no stool samples are required.
For several days before taking the samples, you
must avoid medicines that can interfere with
the results. These include NSAIDs and blood thinners
(see
"Medication precautions," page 35) which can
cause minor stomach bleeding, thereby giving
an abnormal test result. If you have hemorrhoids,
wait until they stop bleeding before doing the
test. Women shouldn't collect stool samples near
the time of menstruation. Finally, avoid using
toilet bowl cleaners for several days before
the test, because these chemicals can affect
the results if they come in contact with your
stool sample.
For several days before the test, you also need
to avoid foods and vitamins that can affect the
test result. Foods to avoid include red meat
(the blood it contains can turn your test positive),
radishes, turnips, cabbage, cauliflower, horseradish,
uncooked broccoli, and cantaloupe (all of which
contain a chemical that can turn the test positive),
and citrus fruits and vitamin C supplements (which
can turn the test falsely negative).
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What
happens when the test is performed?
If one of the traditional tests is used, you
collect three stool samples, ideally on three
different days. Some kits include tissue paper
that you can lay on the surface of the toilet
bowl water to help keep the stool sample from
sinking. As an alternative, you can pass your
bowel movement into a disposable container. Once
you've had a bowel movement, obtain a very small
sample of the stool using the thin wooden sticks
in your kit and smear it on a card from your
kit. Then fold over the card to protect your
sample.When you have all three samples, mail
the cards to the clinic or lab in the plastic-lined
envelope given to you.Make sure that your name
is written on each card.
In the lab, the cards are treated with a chemical
that produces a blue color when blood is present
in the sample. This test works fine no matter
how long it took your samples to reach the lab.
If you have the flush pad test, you drop the
pad into the toilet bowl after you've had a bowel
movement, for three consecutive days. The pads
change color when blood is present in the toilet
bowl. You can flush the toilet to dispose of
the pads, but-if blood is detected-should contact
your doctor.
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What
risks are there from the test?
None.
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Must
I do anything special after the test is over?
No.
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How
long is it before the result of the test is
known?
With the flush pad method, results are available
immediately.With the more traditional methods,
testing is performed in only a few minutes once
the lab receives your sample. Some clinics or
labs do this testing in batches and wait to process
the test until samples have been received from
several people. You should hear from your doctor's
office within a week after the lab has received
your specimen. If your test is positive, it means
you have blood in your stool, and your doctor
will recommend some additional testing to find
out the cause.
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