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Fecal Occult Blood
Fecal Occult Blood
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Fecal Occult Blood
Category: Gastrointestinal system.
Subcategory: Fecal contents.
Material studied: Feces to detect blood.
Estimated cost of test: $8.50.
Patient time for test: Varies. Depends on time it takes to collect three stool specimens.
Reliability of test results: Good.
Available as home self-test? Yes.
Note: Test is particularly important for early diagnosis of bowel cancer; 80% of those with this type of cancer have positive results. Further tests are necessary.
BEFORE THE TEST
Purpose of test:
Detects gastrointestinal bleeding.
Helps confirm early diagnosis of bowel cancer.
Where is test performed?
Commercial laboratory, hospital, doctor's office, home.
Who performs test?
Lab technician, nurse, doctor, you.
Risks and precautions:
Avoid contaminating stool specimen with toilet tissue, urine or menstrual blood.
Send specimen to the laboratory immediately. If transport or testing is delayed more than 30 minutes, refrigerate the specimen.
Patient preparation:
Activity--No changes necessary.
Diet--Eat a high-fiber diet. Do not eat red meat, poultry, fish, turnips or horseradish for 2 to 3 days before the test and during collection period. Avoid eating large amounts of citrus fruit or other vitamin-C-containing foods.
Medicines--Inform the person performing the test if you have recently taken any medications listed under Taking these drugs may affect test results. You may be asked not to take this medication before the test.
Disrobing--None required.
THE TEST
Sensory factors:
Feeling--Some degree of apprehension or fear is normal and should be expected. Discomfort disappears when the test is finished.
Other senses (touch, smell, sight, hearing, taste)--Not affected.
Equipment used:
Tongue blade.
Filter paper.
Specimen container.
Description of test:
See Appendix 12 on collecting a stool specimen.
If you use the available self-test for home use, follow manufacturer's instructions.
Collect three stool specimens.
If you perform your own test, be sure to obtain specimens from two different areas of each stool to allow for variation in blood distribution.
Take stool sample to laboratory for analysis.
AFTER THE TEST
Immediate post-test care:
None.
Activity after test:
Resume normal diet.
Resume taking any medications that were withheld before the test.
Time before test results available:
Test requires only a few minutes in the laboratory. Time before results are reported to the doctor or patient varies from a few minutes to a few days.
TEST RESULTS
Test values:
Test results are determined by color changes on Hematest or Hemoccult tests.
A strongly positive, dark-blue reaction that occurs within 3 to 4 minutes is always abnormal.
A positive dark-blue reaction that appears within 5 minutes is positive for occult blood.
Weakly positive is a faint-blue reaction; it is not necessarily abnormal.
Normal values:
Tests detect less than 2.5ml of blood.
What ABNORMAL may indicate:
A positive test indicates gastrointestinal bleeding.
Varices*.
Peptic ulcer*.
Carcinoma*.
Ulcerative colitis*.
Dysentery*.
Hemorrhagic disease*.
Taking these drugs may affect test results:
Bromides.
Colchicine.
Indomethacin.
Iodides.
Iron preparations.
Phenylbutazone.
Rauwolfia derivatives.
Salicylates.
Steroids.
Vitamin C (ascorbic acid).
Other factors that may affect test results:
Bleeding gums.
Failure to follow dietary restrictions.
Failure to send specimen to the laboratory immediately.
Failure to test specimen immediately.
*See Glossary.
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From Complete Guide to Medical Tests by H. Winter Griffith, M.D. Copyright by Fisher Books. Electronic rights by Medical Data Exchange.
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