Fecal Occult Blood Test

Alternative Names: Guaiac smear test; Fecal occult blood test – guaiac smear; Stool occult blood test – guaiac smear

Definition
The stool guaiac test finds hidden (occult) blood in the stool (bowel movement). It is the most common form of fecal occult blood test (FOBT) in use today.…..click & see

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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.

How the Test is Performed
If the test is performed in an office or hospital, stool may be collected by a doctor during an examination.
If the test is performed at home, a stool sample from three consecutive bowel movements is collected, smeared on a card, and mailed to a laboratory for processing. In order to ensure the accuracy of the guaiac test, follow the manufacturer’s instructions on how to collect the stool.

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. One test kit supplies 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.

For infants and young children wearing diapers, you can line the diaper with plastic wrap. The plastic wrap is positioned so that it keeps the stool away from any urine. Mixing of urine and stool can spoil the sample.

Laboratory procedures may vary. In one type of 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 indicates the presence of blood in the stool.
How do you prepare for the test?
Do not eat red meat, any blood-containing food, cantaloupe, uncooked broccoli, turnip, radish, or horseradish for 3 days prior to the test.

You may need to stop taking medicines that can interfere with the test. These include vitamin C and aspirin. Check with your health care provider regarding medication changes that may be necessary. Never stop or decrease any medication without consulting your health care provider.

For several days before taking the samples, you must avoid medicines that can interfere with the results. These include NSAIDs and blood thinners¬† 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).
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.

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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.

How the Test Will Feel
There is no discomfort when the test is done at home, because this test only involves normal bowel functions. If stool is collected during an exam, there may be some discomfort in the anal canal and rectum.

Why the Test is Performed: This test is a screening test to detect blood in the digestive tract.

Risk Factors: No risk. But there can be false-positive and false-negative results. Using the right collection technique, avoiding certain drugs, and observing food restrictions can reduce errors.

RESULTS:
Normal Results
: –
A negative test result means that there is NO blood in the stool.

What Abnormal Results Mean:-
Abnormal results may indicate:

*Angiodysplasia of the GI tract
*Colon cancer or other gastrointestinal (GI) tumors
*Colon polyps
*Esophageal varices and portal hypertensive gastropathy
*Esophagitis
*Gastritis
*GI infections
*GI trauma or bleeding from recent GI surgery
*Hemorrhoids
*Inflammatory bowel disease
*Peptic ulcer

Stool guaiac testing is sometimes used to screen for colon cancer, but it is not a reliable test for this purpose, and other screening methods should be used.

Additional non-GI related causes of positive guaiac test may include:

*Nose bleed
*Coughing up blood
Abnormal tests require follow-up with your doctor.
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.

Resources:
https://www.health.harvard.edu/fhg/diagnostics/fecal-occult-blood-test.shtml
http://www.nlm.nih.gov/medlineplus/ency/article/003393.htm

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