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What test for fecal occult blood is superior to guaiac testing but is not commonly used clinically?
- In FIT, antibodies to human hemoglobin are collected from venipuncture of rabbits previously exposed to human blood and are coupled to fluorescent proteins for easy detection.
- These antibodies attach to human blood (hemoglobin) in stool and are detected by their fluorescence.
- The FIT test is superior to guaiac tests for detection of colon cancer and colon adenomatous polyps.
- In Japan, patients with a positive FIT screening test undergo colonoscopy as the diagnostic test.
Advantages of FIT Test
- Specific for human hemoglobin, does not recognize cow or other mammalian hemoglobin.
- There are no false positive results with cabbage, cauliflower, or broccoli (pseudoperoxidase).
- Hemoglobin released from UGI tract bleeding is digested, and is not immune reactive to FIT.
