Is Fecal Immunochemical Test (FIT) positivity an indication to perform colonoscopy in a patient with a previously established bleeding peptic ulcer?

FIT Positivity in Patients with Previously Established Bleeding Peptic Ulcer: Indications for Colonoscopy

A positive Fecal Immunochemical Test (FIT) in a patient with a previously established bleeding peptic ulcer is not an automatic indication for repeat colonoscopy, as the positive result is likely due to the known upper GI source rather than a new colonic lesion.

Understanding FIT Testing and Its Limitations

FIT is designed to detect human globin, a component of hemoglobin that is more specific for lower gastrointestinal bleeding than older guaiac-based tests. However, it's important to understand several key characteristics of FIT:

• FIT is more specific for lower GI bleeding because globin is degraded by digestive enzymes in the upper GI tract 1
• Despite this increased specificity, upper GI sources can still cause positive FIT results, especially with active bleeding
• A positive FIT has high positive predictive value for significant neoplasia in screening populations, but this is not applicable in patients with known bleeding sources

Management Algorithm for FIT Positivity in Patients with Previous Peptic Ulcer Bleeding

Step 1: Assess the clinical context

• Determine time since last documented peptic ulcer bleeding
• Evaluate for signs/symptoms suggesting active or recurrent peptic ulcer bleeding
• Check for presence of anemia or changes in hemoglobin levels

Step 2: Decision pathway based on clinical assessment

If patient has signs of active upper GI bleeding:

• Proceed directly to upper endoscopy (EGD) rather than colonoscopy
• Early EGD (within 24 hours) significantly increases the rate of finding the bleeding focus (82% vs. 73%) and enables endoscopic hemostasis (32% vs. 12%) compared to delayed EGD 2

If patient is clinically stable without overt bleeding:

• According to the US Multi-Society Task Force on Colorectal Cancer, the decision to perform colonoscopy should consider:
  • Clinical context (other worrisome signs/symptoms)
  • Patient factors (risk factors for advanced neoplasia)
  • Prior colonoscopy quality and timing 1

Key Considerations

1. Source of bleeding: Peptic ulcers are a common and well-established cause of GI bleeding, accounting for a significant proportion of upper GI bleeds 1

2. Timing of previous evaluation: If the patient has had a recent high-quality colonoscopy with good preparation, repeating it based solely on FIT positivity may not be warranted

3. Risk factors: Consider patient-specific risk factors that might increase the likelihood of a colonic source:

   • Age
   • Family history of colorectal cancer
   • Personal history of colonic polyps
   • Concurrent medications (NSAIDs, anticoagulants)

Common Pitfalls to Avoid

1. Automatic colonoscopy: Performing colonoscopy in every patient with FIT positivity and known peptic ulcer disease without considering clinical context may lead to unnecessary procedures

2. Ignoring upper GI sources: Remember that a positive FIT can result from upper GI bleeding, especially with active bleeding

3. Poor bowel preparation: If colonoscopy is deemed necessary, adequate bowel preparation is crucial as inadequate preparation significantly reduces diagnostic yield, particularly in early colonoscopy for lower GI bleeding 2

Conclusion

When evaluating a positive FIT in a patient with previously established bleeding peptic ulcer, the clinician should first consider whether the positive result is likely due to the known upper GI source. In most cases, especially with recent or active peptic ulcer bleeding, the FIT positivity can be attributed to the upper GI source, and colonoscopy may not be indicated unless there are other concerning features or the patient is due for routine colorectal cancer screening.