Occult Blood in Stool
- Description: Some diseases of the intestines can result in the passage of blood in the stool. Small amounts of blood are not visible in the stool. Special chemicals can be applied to stool samples in order to allow for detection of small amounts of blood (occult blood). The stool sample can be obtained by a doctor, nurse, or the patient at a hospital, doctor’s office, or at home. The results are interpreted by a doctor, lab technician, or nurse. The test takes minutes to perform, both in collecting the stool and applying the chemical.
- Discomfort – Minimal or no discomfort; although, obtaining the stool specimen is unpleasant.
- Results – Immediately, or 1-2 days if the results are interpreted at a lab.
- Risks of Procedure – None.
- Other Names – Heme occult, fecal occult blood test (FOBT).
Indications for the Test
- To identify blood in the stool as a manifestation of disease in the intestines.
- To screen for colorectal cancer.
- The test can be made to show a false positive result by various compounds. You may be advised to avoid aspirin or aspirin substitutes, iron supplements, alcohol, or foods such as red meats, citrus fruits, bean sprouts, turnips, radishes, mushrooms or artichokes.
- Stool samples are collected by digital rectal exam in the hospital or doctor’s office.
- Stool samples are collected at the patient’s home by the patient. A sample is obtained with the use of an applicator stick and applied to the cards as directed.
- The stool cards are then developed at a doctor’s office or lab.
After the Procedure
- You are free to resume normal activities.
Factors Affecting Results
- Hemorrhoids, menstrual bleeding, or one of the compounds listed above may cause false-positive results.
- The test can detect minute amounts of blood in the stool.
- The test is inexpensive.
- The test can be performed at home.
- The cause of the blood in the stool is not made apparent from the test.
- False positive results are common.
- Collecting stool specimens is unpleasant.