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Alternative Names: Fecal Occult Blood Test, FOBT.
Amounts of blood that come from the digestive system but are too small to be seen can be detected chemically. The detection of such small amounts of blood ('hidden', or 'occult' blood) may provide early clues to the presence of ulcers, cancers, and other abnormalities.
Bleeding in the digestive system can be caused by something as insignificant as a little irritation or as serious as cancer. When bleeding is profuse, a person can vomit blood (hematemesis), pass bright red blood in the stool (hematochezia), or pass black, tarry stool (melena).
Function; Reasons For Use
There are two types of test:- The traditional guaiac smear test (also called Hemoccult, Seracult, or Coloscreen) is completed and interpreted by a medical professional; these tests are usually only available from a laboratory or a doctor's office.
- The newer, flushable reagent pads (EZ DetectT, ColoCARE). These are available without a prescription at many drugstores.
Many patients prefer the flushable reagent pads because there is no stool handling, more privacy, and no laboratory processing. However, health care providers usually favor the guaiac tests because the large studies that have shown the benefits of colon cancer screening were done with guaiac tests.
Guaiac Smear Test. During a rectal examination, the doctor obtains a small amount of stool on a gloved finger. This sample is placed on a piece of filter paper impregnated with a chemical (guaiac). After another chemical is added, the color of the sample will change if blood is present. Alternatively, the person can take home a kit containing the impregnated filter papers. The person places samples of stool from about three different bowel movements on the filter papers, which are then mailed in special containers back to the doctor for testing. If blood is detected, further examinations are needed to determine the source.
These tests are useful in detecting hidden blood in the stool, and are mainly used for colorectal cancer screening. They may also be performed in the evaluation of anemia.
Positive test results may also indicate the following:Note that false positives are common.
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Occult Blood Tests can help with the following:
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GLOSSARY
Anemia (Anaemia, Anemias)
A condition resulting from an unusually low number of red blood cells or too little hemoglobin in the red blood cells. The most common type is iron-deficiency anemia in which the red blood cells are reduced in size and number, and hemoglobin levels are low. Clinical symptoms include shortness of breath, lethargy and heart palpitations.
Cancer
Refers to the various types of malignant neoplasms that contain cells growing out of control and invading adjacent tissues, which may metastasize to distant tissues.
Colon (Colonic)
The part of the large intestine that extends to the rectum. The colon takes the contents of the small intestine, moving them to the rectum by contracting.
Colorectal Cancer
A cancerous tumor of the large intestine. It is marked by dark, sticky stools containing blood and a change in bowel habits.
Esophagus (Esophageal)
Commonly called the "food pipe", it is a narrow muscular tube, about nine and a half inches long, that begins below the tongue and ends at the stomach. It consists of an outer layer of fibrous tissue, a middle layer containing smoother muscle, and an inner membrane, which contains numerous tiny glands. It has muscular sphincters at both its upper and lower ends. The upper sphincter relaxes to allow passage of swallowed food that is then propelled down the esophagus into the stomach by the wave-like peristaltic contractions of the esophageal muscles. There is no protective mucosal layer, so problems can arise when digestive acids reflux into the esophagus from the stomach.
Gastritis
Inflammation of the stomach lining. White blood cells move into the wall of the stomach as a response to some type of injury; this does not mean that there is an ulcer or cancer - it is simply inflammation, either acute or chronic. Symptoms depend on how acute it is and how long it has been present. In the acute phase, there may be pain in the upper abdomen, nausea and vomiting. In the chronic phase, the pain may be dull and there may be loss of appetite with a feeling of fullness after only a few bites of food. Very often, there are no symptoms at all. If the pain is severe, there may be an ulcer as well as gastritis.
Gastrointestinal (GI, GI Tract)
Pertaining to the stomach, small and large intestines, colon, rectum, liver, pancreas, and gallbladder.
Hemorrhoids
Varicose disorder causing painful swellings at the anus; piles.
Peptic Ulcer (Duodenal Ulcer, Duodenal Ulcers, Gastric Ulcer, Gastric Ulcers, Peptic Ulcers)
A general term for gastric ulcers (stomach) and duodenal ulcers (duodenum), open sores in the stomach or duodenum caused by digestive juices and stomach acid. Most ulcers are no larger than a pencil eraser, but they can cause tremendous discomfort and pain. They occur most frequently in the 60 to 70 age group, and slightly more often in men than in women. Doctors now know that there are two major causes of ulcers: most often patients are infected with the bacteria Helicobacter pylori (H. pylori); others are regular users of non-steroidal anti-inflammatory drugs (NSAIDS), which include common products like aspirin and ibuprofen.
Polyp (Polyps)
A usually nonmalignant growth or tumor protruding from the mucous lining of an organ such as the nose, bladder or intestine, often causing obstruction.
Ulcer (Ulceration, Ulcers)
Lesion on the skin or mucous membrane.
Last updated: Oct 08, 2008
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