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Fecal Occult Blood Testing

Which Test?



Fecal Occult Blood Tests

Slide 4

October 2011

Because occult blood is not visible….a stool blood test is required to detect it. There are essentially 3 types of fecal occult blood tests, and it is important to understand how they differ. Guaiac tests (like Hemoccult) 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. The fecal immunochemical test (often referred to as FIT) specifically detects the globin portion of human hemoglobin, and is less affected by diet or medications. However, globin is rapidly digested in the upper GI tract which compromises the use of FIT for global detection of occult bleeding. Porphyrin-based tests (like HemoQuant) target both heme and heme-derived porphyrins, are not affected by anatomic site of bleeding, and are quantitative. In contrast, both other types of tests are insensitive for upper GI bleeding because of analyte digestion. For all 3 types of tests, performance in the laboratory is recommended, and I will elaborate further on this point. While the laboratory costs and test pricing vary, Medicare reimburses each at the same $22 rate. Typically, results from both Guaiac and FIT tests are available either the same or next day; HemoQuant results are usually reported the following day.

Fecal Occult Blood Tests

 


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