Download Fecal Occult Blood Test (FOBT)

Fecal Occult Blood Test (FOBT)
Introduction
A fecal occult blood test is used to screen patients for colorectal
cancer. The test helps detect the presence of hidden blood in
the stool, which is one of the first warning signs that a patient
may have colorectal cancer.
Your doctor may ask you to have a fecal occult blood test, or
FOBT. This reference summary explains why the test may be
performed, how it is performed, and how its results are
interpreted.
Colorectal Cancer
The FOBT is most often used to screen patients for colon
cancer. This section gives you some information about the
disease.
Cancer that occurs in the colon or rectum is called
colorectal cancer. The colon is the large intestine; the
rectum is the end of the digestive tract from where stool is
excreted through the anus.
Colorectal cancer is second only to lung cancer as the
leading cause of cancer-related death in the United States.
In 2008, it’s estimated that colorectal cancer will cause
nearly 49,000 deaths in the United States.
Colon
and Rectum
The earlier colorectal cancer is detected, the more
successfully it can be treated.
This document is for informational purposes and is not intended to be a substitute for the advice of a doctor or healthcare professional or a
recommendation for any particular treatment plan. Like any printed material, it may become out of date over time. It is important that you rely on the
advice of a doctor or a healthcare professional for your specific condition.
©1995-2013, The Patient Education Institute, Inc. www.X-Plain.com
Last reviewed: 02/21/2013
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Polyps and cancers tend to grow slowly and may bleed from time to time (Polyp is a
mass of tissue projecting outside the inner membrane of the digestive tract. It is like a
small grape in shape). Sometimes this blood is visible in a patient’s stool; other times it
is not. Hidden blood in the patient’s stool can often be detected by a screening test like
FOBT, which may give a warning sign regarding potential colorectal cancer.
Fecal means stool, occult means not seen by the naked eye. Therefore, a fecal occult
blood test, or FOBT, detects blood in the stool that cannot be seen by the naked eye. If
an FOBT detects blood, however, this does not necessarily mean you have colorectal
cancer. Many factors can cause blood in the stool. Your doctor will order additional
tests to diagnose the cause of the bleeding.
How to Prepare
Because colon cancers may bleed only from time to time, the FOBT tests three
separate bowel movements over a period of several days. This increases the chance
of detecting small amounts of blood in your stool.
Some foods can cause the results of FOBT to be a “false positive,” which means it
appears that there is blood in the patient’s stool even
though there is no blood in the stool. You need to
avoid these foods 2 to 3 days before the test: turnips,
beets, radishes, horseradish, artichokes, mushrooms,
broccoli, bean sprouts, cauliflower, apples, oranges,
bananas, grapes and melon.
The blood in red meat may also cause blood to appear
in a patient’s stool. Therefore, you should avoid red
meat 2 to 3 days before the test.
Iron supplements, aspirin, and Vitamin C can also
affect the results. Avoid them before the test.
Your doctor may ask you to stop some medications that could affect the FOBT test
results. These include colchicine, iodine, antacids or boric acid.
If you have your menstrual period or have bleeding hemorrhoids, do not take the
FOBT.
This document is for informational purposes and is not intended to be a substitute for the advice of a doctor or healthcare professional or a
recommendation for any particular treatment plan. Like any printed material, it may become out of date over time. It is important that you rely on the
advice of a doctor or a healthcare professional for your specific condition.
©1995-2013 The Patient Education Institute, Inc. www.X-Plain.com
Last reviewed: 02/21/2013
ge200103
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How it is Done
The fecal occult blood test (FOBT) is one type of colorectal screening test. The test
can be conducted in a doctor’s office or at the patient’s home. A small sample of stool
is placed on a chemically treated card, pad, or wipe; then a chemical developer
solution is put on top of the sample. If the card, pad, or cloth turns blue, there is blood
in the stool.
The procedure for testing blood in the stool varies depending on which type of home
test you have. It is important to follow the manufacturer's instructions provided with its
test. Always check the expiration date on the package. Read the instructions that come
with your test carefully and follow the directions exactly. For most tests, you will use
stool samples from three different bowel movements over three different days. It can
be unpleasant to collect a stool sample. However, the test has no risk and is an
effective way to screen for cancer.
Note: Products that are used to clean or deodorize the toilet may contaminate the
FOBT testing kit. Repeat the test if the stool sample card touches the toilet seat or
other objects that have such chemicals.
Results
If the card turns blue, this means there may be blood in you
stool. This is called a positive test, or abnormal results.
If the card does not turn blue, this means no blood was detected
in your stool. This is called a negative test, or normal results.
If your FOBT results are abnormal or the test is positive, your
doctor will order follow-up tests to check for the causes of
bleeding, if any bleeding is confirmed. Follow-up tests may
include colonoscopy, upper GI endoscopy or sigmoidoscopy:
• Colonoscopy is the examination of the colon with an
endoscope. The endoscope is a long thin tube topped with a camera that allows
the doctor to see inside the colon.
• Endoscopy is the examination of the upper digestive system with an endoscope.
The endoscope is a long thin tube topped with a camera that allows the doctor to
see inside the colon.
• Sigmoidoscopy is the examination of the last part of the large colon with a scope.
The scope allows the doctor to see inside the colon.
This document is for informational purposes and is not intended to be a substitute for the advice of a doctor or healthcare professional or a
recommendation for any particular treatment plan. Like any printed material, it may become out of date over time. It is important that you rely on the
advice of a doctor or a healthcare professional for your specific condition.
©1995-2013 The Patient Education Institute, Inc. www.X-Plain.com
Last reviewed: 02/21/2013
ge200103
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If the FOBT is positive and additional testing does not find blood in the stool, this
means the original test was incorrect, or a “false positive.” Because many foods and
medicines affect FOBT results, don’t be anxious yet if you have a positive FOBT. Wait
for follow-up testing to confirm it was a “true positive.” The test may have been affected
by another condition, or food you ate.
If the FOBT is positive and additional testing confirms blood in the stool, this means
the original test was correct, or a “true positive.” This still does not mean the patient
has cancer. In fact, the majority of patients who have a “true positive” FOBT have
bleeding in the digestive system that is not caused by cancer.
If the FOBT is negative but later on other tests find blood in the stool, this means the
original test was a “false negative.” Because early colorectal cancer does not bleed all
the time and some colon cancers do not bleed, an FOBT may be negative when the
patient actually has cancer. That is why your doctor may recommend repeated testing
over time.
Conclusion
A fecal occult blood test is a screening test that helps to detect the presence of hidden
blood in the stool. It is mostly used to screen for colorectal cancer. The test can be
performed at home. If the card on which the stool sample is placed turns blue, the
FOBT is positive, which means traces of blood were found in the stool.
If an FOBT detects blood in your stool, contact your healthcare provider; you may need
additional tests, such as a colonoscopy, upper GI endoscopy or sigmoidoscopy, to
confirm the bleeding and find its cause. In most cases, the bleeding is caused by
medical conditions other than cancer. The FOBT screens for colorectal cancer but
does not diagnose it.
Many foods and medications can affect an FOBT, causing it to
be positive. Prepare for the FOBT test by halting the
consumption of such foods and medications.
The earlier we detect colorectal cancer, the more successfully
we can treat it. Regular FOBT screening saves lives. Your
doctor can recommend how frequently you should have the
test, which depends on your age and your risk factors.
This document is for informational purposes and is not intended to be a substitute for the advice of a doctor or healthcare professional or a
recommendation for any particular treatment plan. Like any printed material, it may become out of date over time. It is important that you rely on the
advice of a doctor or a healthcare professional for your specific condition.
©1995-2013 The Patient Education Institute, Inc. www.X-Plain.com
Last reviewed: 02/21/2013
ge200103
4