What is a guaiac test?

A guaiac test is a diagnostic tool used to evaluate fecal matter in an effort to detect abnormalities associated with dysfunction of the gastrointestinal tract. Assessed for the presence of blood, fecal occult blood test (FOBT) samples can be collected by the individual at home or by a health care provider in a medical setting, such as a doctor's office or clinic. The test often requires preparatory steps on the part of the individual and these should be discussed with a qualified health care provider when scheduling the test. Administration of a guaiac test carries some risk of false results due to the potential for insufficient sample collection or contamination.

In general, a guaiac test is done to detect bloody stools that often occur in the presence of gastrointestinal problems. Abnormal results showing the presence of blood may be indicative of colon problems, including polyps and tumors, gastrointestinal infection, and inflammatory bowel disease. Other conditions that can trigger bloody stools include hemorrhoids, ulcers, and various colonic malignancies. Any indication of abnormalities usually requires additional tests to further evaluate the source of the bleeding.

People scheduled for a guaiac test may be given specific instructions that often contain dietary restrictions. Certain raw vegetables, such as radish and broccoli, should be avoided due to their ability to cause gas and diarrhea. The consumption of any red meat is commonly discouraged due to its natural blood content which can lead to sample contamination. The duration and specific content of preparatory diet changes vary and should be discussed with a health care provider during consultation.

The method of stool collection used often depends on the age of the individual and the setting in which the collection takes place. Home collection techniques are non-invasive, do not induce any discomfort, and take place over a period of time. Those who undergo a guaiac test during the course of a physical exam performed in a medical setting may experience some discomfort. Due to the invasive nature of this type of sample collection, irritation of the lower gastrointestinal tract may occur.

When performing a guaiac test at home, a special kit may be used that contains all the collection materials needed to obtain stool samples. The use of plastic wrap or special tissues is often used to obtain samples to avoid cross-contamination. Sample collection involving young children, especially those still in diapers, requires precautionary measures to reduce the risk of urine-contaminated samples. Strict adherence to the supplied instructions is essential to ensure correct sample collection and submission. The samples obtained are usually mailed to a laboratory or delivered to a medical facility for testing.

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