Occult Blood, Feces, Diagnostic

Qualitative screening for detecting fecal occult blood which may be indicative of gastrointestinal disease.

When Guaiac test is preferred:

• Iron Deficiency, Anemia and suspected Upper GI Bleed:
  • The majority of pathologic occult GI bleeding arises from the upper GI tract, nearly twice as often as from the lower GI tract.
  • Guaiac stool tests are capable of detecting Upper GI Bleeds.

When FIT test is preferred:

• Colorectal Cancer Screening:
  • Studies have suggested that immunochemical tests, compared to stool guaiac tests, may have better performance characteristics for colorectal cancer screening, with increased sensitivity without loss of specificity. Patient willingness to be tested may also be higher with FIT compared to screening by stool guaiac, flexible sigmoidoscopy, or colonoscopy.

The American College of Gastroenterology supports the joint guideline recommendation that the older guaiac-based fecal occult blood testing be abandon as method for CRC screening.

Guaiac tests (like Hemoccult Sensa) develop a blue color in the presence of heme or other peroxidase-like or oxidizing compounds. It is a nonspecific reaction that can be influenced by a number of foods and medications.