Stool guaiac test

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It involves feces, a thick piece of paper attached to a thin film coated with guaiac (which comes from the Guaiacum tree [cite web | url = http://www.fda.gov/cdrh/oivd/guidance/772.html#5a | title = Guidance for Industry and FDA Staff - Review Criteria for Assessment of Qualitative Fecal Occult Blood In Vitro Diagnostic Devices | date = August 8, 2007 | publisher = United States Food and Drug Administration Office of In Vitro Diagnostic Device Evaluation and Safety] ), and hydrogen peroxide. Either the patient or medical professional smears a small fecal sample onto the film, drips one or two drops of peroxide on the film, and observes for a color change.

The fecal sample can be obtained either by wiping soiled toilet tissue on the film or, more frequently in medical settings, it's obtained either with a gloved finger (with a digital rectal exam) or with a wooden stick dipped into stool. Only a small sample for smearing is necessary; a large sample of stool would actually impede an accurate test.

When the hydrogen peroxide is dripped onto the guaiac, it oxidizes the guaiac causing a color change. This oxidation occurs very slowly. Heme, a component of hemoglobin found in blood, catalyzes this reaction, giving a result in about 2 seconds. Therefore, a positive test result is one where there is a quick color change of the film.

A positive FOBT may be followed by: 1.Sigmoidoscopy: an examination of the rectum and lower colon with a lighted instrument to look for abnormalities, such as polyps. 2.Colonoscopy: a more thorough examination of the rectum and entire colon. 3.Double contrast barium enema: a series of x-rays of the colon and rectum.

References

External links

*cite web|url=http://www.nlm.nih.gov/medlineplus/ency/article/003393.htm|title=Medline Plus: stool guaiac test|work=National Institute of Health|accessdate=2007-01-05