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

Recommended Stool Studies in Crohn's Disease and Gastritis Workup

All patients presenting with suspected or worsening Crohn's disease or gastritis should have stool cultures for entero-invasive bacterial infections and stool Clostridioides difficile assay as part of their initial workup. 1

Essential Stool Studies

For Initial Diagnosis

• Stool cultures for entero-invasive bacterial infections 1
• Clostridioides difficile assay (toxin testing) 1, 2
• Fecal calprotectin - helps differentiate IBD from IBS with high sensitivity (93%) and specificity (96%) 1
• Fecal lactoferrin - aids in differentiating IBD from functional disorders 1

For Disease Flares/Worsening Symptoms

• Stool cultures for microscopy and culture 1
• Clostridioides difficile toxin assay - particularly important as C. difficile is present in up to 20% of IBD flares 1, 3
• Fecal calprotectin - for monitoring disease activity (values >150 mg/g suggest active inflammation) 1, 2

For Patients with Relevant Travel History

• Microscopy and culture for amoebic or Shigella dysentery 1
• Testing for ova, cysts, and parasites according to local policies and travel history 1
• Consider single stool specimen for ova and parasite examination (detects 91% of parasites) 4

Special Considerations

For Immunosuppressed Patients

• CMV testing - patients with moderate to severe colitis, particularly those with steroid-refractory disease, should have colonic biopsies for CMV by immunohistochemistry or PCR 1
• Consider multiplex PCR panels - higher detection rates of pathogens (26% vs 5% with conventional testing) and associated with less unnecessary escalation of IBD therapy 5

For Patients with Recent Antibiotic Use

• C. difficile testing is essential - 90% of C. difficile positive tests in IBD flares are associated with antibiotic use in the prior month 3
• Vancomycin or fidaxomicin are recommended for 10 days for treating non-severe C. difficile infection 1, 2

Clinical Pearls and Pitfalls

• Pitfall: Failing to test for C. difficile in all IBD flares. C. difficile infection in IBD contributes to higher rates of colectomy, postoperative complications, and mortality 1
• Pitfall: Escalating immunosuppressive therapy in the setting of undiagnosed C. difficile infection 1, 2
• Pearl: IBD patients may have undiagnosed C. difficile infections that contribute to dysregulated immunity and inflammation 6
• Pearl: Antibiotic use is significantly associated with positive C. difficile toxin, and toxin-positive patients typically improve with targeted antibiotics 3

Testing Algorithm

1. For all new diagnoses and flares:

   • Stool culture and C. difficile toxin assay 1
   • Fecal calprotectin 1

2. If symptoms persist despite negative initial tests:

   • Consider CMV testing via colonic biopsies 1
   • Consider multiplex PCR panel for broader pathogen detection 5

3. For patients with upper GI symptoms:

   • Consider upper endoscopy with biopsies, as Crohn's disease can present with gastritis 7

4. For patients with steroid-refractory disease:

   • Colonic biopsies for CMV immunohistochemistry or PCR from actively inflamed areas 1

By following this comprehensive stool testing approach, clinicians can better differentiate between infectious causes and true IBD flares, leading to more appropriate treatment decisions and improved patient outcomes.