From the Guidelines
The statement is partially accurate, as FIT (fecal immunochemical test) is not the same as fecal occult blood testing (FOBT), although both detect blood in stool. FIT specifically detects human hemoglobin using antibodies and is more specific for lower gastrointestinal bleeding, whereas traditional guaiac-based FOBT detects the peroxidase activity of heme and can be affected by diet and medications 1.
Key Differences Between FIT and FOBT
- FIT is more sensitive for detecting colorectal cancer and doesn't require dietary restrictions before testing.
- FOBT can produce false positives due to dietary factors or certain medications.
- The choice between FIT and FOBT may depend on the clinical context and patient factors.
Clinical Scenario
In this clinical scenario, ordering a FIT test is appropriate to check for occult blood that might indicate a more serious cause of bleeding beyond the visible blood already noted. The test complements the plan to refer the patient for a screening colonoscopy, which is indicated based on her age and symptoms, as suggested by the USPSTF recommendation for adults aged 50 to 75 years 1.
Recommendations
- The patient should undergo the ordered FIT test to rule out occult blood.
- A high fiber diet and increased water intake are recommended to help manage symptoms.
- The referral for a screening colonoscopy is appropriate given the patient's age and presentation with rectal bleeding.
From the Research
Definition and Comparison of FIT and Fecal Occult Blood Tests
- FIT (Fecal Immunochemical Test) and fecal occult blood tests are both used for colorectal cancer screening, but they are not exactly the same 2, 3, 4.
- Fecal occult blood tests (FOBT) measure the presence of blood in stool using guaiac-based tests or fecal immunochemical tests (FIT) 2.
- FIT is a type of FOBT that specifically measures human hemoglobin in stool, offering higher sensitivity and specificity than traditional guaiac-based FOBTs 3, 4.
Advantages of FIT over Traditional Fecal Occult Blood Tests
- FIT has several advantages over guaiac-based FOBTs, including higher sensitivity and specificity, improved clinical performance, and higher efficiency 2, 3, 4.
- FIT can be automated, and the cut-off for a positive result can be adjusted, making it more flexible than traditional FOBTs 2, 3.
- FIT is also easier to use, resulting in higher acceptance rates and better detection of advanced adenomas and colorectal cancer 3, 4.
Clinical Application and Recommendations
- The use of FIT for colorectal cancer screening is supported by evidence and widely recommended by guidelines 5, 6.
- FIT is considered a superior test to traditional FOBTs for colorectal cancer screening, especially in scenarios where maximizing participation and detection of advanced neoplasia are prioritized 4, 6.
- Recommendations on the application of FIT for colorectal cancer screening have been developed, including guidance on test implementation and quality metrics for program evaluation 6.