Management of Positive Colon Guard (FIT) Test Results
When a patient has a positive Fecal Immunochemical Test (FIT) result, prompt referral for colonoscopy is strongly recommended as the definitive next step in evaluation. 1
Rationale for Colonoscopy After Positive FIT
A positive FIT has high positive predictive value for significant colorectal neoplasia, making timely follow-up essential:
- Colonoscopy is the only structural examination that both directly evaluates the entire colorectal mucosa and allows for simultaneous removal of significant neoplasia 1
- The US Multi-Society Task Force on Colorectal Cancer provides a strong recommendation with moderate-quality evidence for colonoscopy as the recommended test following a positive FIT 1
Timing of Colonoscopy
The timing of colonoscopy after a positive FIT is critical:
- Ideally, colonoscopy should be performed within 30 days of a positive FIT result 1
- Delays in colonoscopy of 6 months or longer after a positive FIT are associated with:
Quality Considerations for Colonoscopy
To maximize diagnostic yield:
- Colonoscopy should be complete to the cecum and of high quality 1
- High-quality preparation is essential for optimal colonic mucosal visualization 1
- The procedure should be performed by an experienced endoscopist with adequate adenoma detection rates
Special Considerations
Patients with Recent Prior Colonoscopy
For patients with a positive FIT who have had a recent colonoscopy:
- Generally, repeat colonoscopy should still be offered due to FIT's superior performance characteristics compared to older testing methods 1
- Consider factors such as:
- Clinical context (other concerning signs/symptoms)
- Patient risk factors for advanced neoplasia
- Quality of the previous colonoscopy (bowel preparation, endoscopist's adenoma detection rate) 1
Medications
- Unlike older guaiac-based tests, FIT results are not affected by dietary intake 1
- Patients do not need to adjust diet or medications (including anticoagulants or antiplatelet agents) before completing a FIT test 1, 2
- While medications like anticoagulants may increase FIT positivity rates 3, this represents true bleeding that still warrants investigation
Common Pitfalls to Avoid
Assuming hemorrhoids are the cause of a positive FIT: The US Multi-Society Task Force notes that hemorrhoids alone should not be assumed to be the cause of a positive FIT without colonoscopy 2
Using FIT for symptomatic patients: For patients with alarming symptoms (hematochezia, unexplained iron deficiency anemia, unexplained weight loss), diagnostic colonoscopy remains the modality of choice rather than FIT testing 1
Delayed follow-up: Only 44% of patients with positive fecal occult blood tests undergo full colon evaluation within 12 months in some studies 4, highlighting the importance of systems to ensure timely follow-up
Upper GI evaluation: In the absence of iron-deficiency anemia or signs/symptoms of upper GI pathology, a positive FIT and negative colonoscopy should not automatically prompt upper GI evaluation 1
Improving Adherence to Follow-up
To maximize follow-up rates:
- Programs should aim for ≥95% of follow-up colonoscopies to be performed within 6 months of a positive test 1
- Patient outreach should be attempted within 2 weeks of positive test results 1
- CRC system-level navigation programs that track test-positive patients and contact them by telephone to schedule appointments can increase adherence 1
Conclusion
A positive FIT result requires prompt referral for colonoscopy, ideally within 30 days and no later than 6 months after the positive result. Proper follow-up is essential to realize the mortality benefits of colorectal cancer screening programs.