Fecal Occult Blood Screening

1 December 2014
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Gamma Healthcare Implements Immunoassay Format for Fecal Occult Blood Screening

November 24, 2014:

The National Institutes of Health reports that colorectal cancer is one of the leading causes of cancer deaths in the United States 1. The good news is that a complete cure can be achieved with early diagnosis. Often times, colon cancer will have no symptoms but when symptoms are present they may include abdominal pain and tenderness, blood in the stool, diarrhea, narrow stools, or weight loss for no apparent reason 1. Through screening tests such as the fecal occult blood test by immunoassay (iFOBT), colon cancer can be detected prior to the development of many of these symptoms.

The fecal occult blood test by immunoassay our laboratory employs will detect small amounts of blood in the stool. More specifically, the immunological based test is designed to detect human hemoglobin in a patient’s stool with few, if any, interfering substances 2. This is in sharp contrast to the conventional guaiac method, which tests for the presence of peroxidase activity in a patient’s stool with results subject to many interfering substances often leading to a false positive or false negative result. Fewer false positive results means fewer interventional procedures performed in patients without disease 2.

In the best interests of our patients, earlier this year we launched the immunoassay methodology for fecal occult blood testing. Traditional guaiac testing is no longer available. The following chart outlines the advantages of immunoassay over peroxidase testing.

Why iFOBT 2:

Annual Detection Test

iFOBT Screening

Conventional Guaiac Test

Test Procedure

One sample from one bowel movement

Three samples from three separate bowel movements

Dietary Restrictions


Meat, certain vegetables, fruit and certain supplements (i.e. Vitamin C) three days prior

Medicinal Restrictions


Nonsteroidal anti- inflammatory drugs, such as ibuprofen, naproxen or aspirin one-week prior

A special collection device is required and must be used at the time of collection. Specimens are stable at room temperature for up to 8 days or up to 14 days if refrigerated.

This immunological assay can only be performed on feces. Occult blood testing on urine, gastric contents, or other body fluids will require an alternative methodology. Patients with hemorrhoids or menstrual bleeding should not consider testing until bleeding ceases. Do not collect a fecal specimen contaminated with urine or toilet bowl water as erroneous results may result.


  1. Chen, Y., Zieve, D., & Black, B. (2013). Colon Cancer. Medline Plus: A service of the U.S. National Library of Medicine. National Institutes of Health. Retrieved November 24, 2014 from http://www.nlm.nih.gov/medlineplus/ency/article/000262.htm.
  2. Procedure manual. (n.d.). OC-AUTO Micro 80. Polymedco, Inc. Retrieved November 24, 2014 from http://www.polymedco.com/product-overview-oc-auto-micro-80-pages- 53.php.


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