What stool studies are recommended in the workup for gastritis and Crohn's disease?

Recommended Stool Studies in Gastritis and Crohn's Disease Workup

In the workup for gastritis and Crohn's disease, stool studies should include fecal calprotectin, stool cultures, and Clostridioides difficile testing to evaluate inflammation and rule out infectious causes. 1

Essential Stool Studies

Inflammatory Markers

• Fecal calprotectin: Critical biomarker for assessing IBD activity with high sensitivity (93%) and specificity (96%) for differentiating IBD from non-IBD conditions 1
• Fecal calprotectin levels >150 mg/g suggest active inflammation and can help differentiate between infection and IBD flare 2
• Values <100 μg/g suggest endoscopic remission, while values >250 μg/g indicate a low likelihood of endoscopic remission and need for further evaluation 1

Infectious Disease Testing

• Stool cultures: Mandatory to exclude infectious causes that may mimic or trigger IBD symptoms 1
• C. difficile toxin testing: Essential in all patients with suspected IBD flares as C. difficile infection can mimic or trigger IBD symptoms 1, 2
• Testing for other enteric pathogens (e.g., norovirus, Campylobacter) is recommended as Crohn's patients have higher risk of concurrent infections 2

Clinical Algorithm for Stool Testing

Initial Diagnostic Workup

1. All suspected IBD patients: Order fecal calprotectin, stool cultures, and C. difficile toxin test 1
2. Interpret fecal calprotectin results:
   • <100 μg/g: Continue current therapy (if established patient) or consider other diagnoses (if new patient) 1
   • 100-250 μg/g: Intermediate probability of active disease; consider repeating in 6 weeks 1

   • 250 μg/g: High likelihood of active inflammation; proceed with endoscopic evaluation 1

During Disease Flares

1. Always test for C. difficile before escalating immunosuppressive therapy 2
2. Monitor fecal calprotectin to differentiate between ongoing infection and IBD flare 2
3. Repeat stool studies if symptoms persist despite appropriate treatment 1

Diagnostic Considerations

Gastritis-Specific Considerations

• H. pylori testing should be considered, though H. pylori-positive gastritis is relatively rare in Crohn's disease patients (8.4%) 3
• H. pylori-negative gastritis is more common in Crohn's disease (28.6-32%) and may represent Crohn's gastritis 4, 3

Crohn's Disease Considerations

• Fecal calprotectin has greater diagnostic precision with a cut-off of 100 μg/g compared to 50 μg/g 1
• Consider upper GI endoscopy only in patients with upper GI symptoms, as routine gastroscopy is not indicated in adults with suspected Crohn's disease 1

Common Pitfalls to Avoid

• Don't rely solely on CRP: Approximately 20% of patients with active Crohn's disease may have normal CRP levels 1
• Don't escalate immunosuppressive therapy without ruling out C. difficile infection in patients with worsening symptoms 2
• Don't forget to test for other enteric pathogens besides C. difficile, especially in immunosuppressed patients 2
• Don't interpret normal fecal calprotectin as definitive absence of disease without considering clinical context and other markers 1