Clostridioides (Clostridium) difficile Testing, Stool (LAB4886)

There is no test for C. difficile infection. Testing for GDH antigen/toxin has high negative predictive value, while positive results may indicate true infection or colonization.  

Clinical Background
  • Clostridioides difficile infection (CDI) is a common nosocomial infection. 
  • Only individuals who present with 3 or more unformed stools within 24 hours, in a setting of unexplained and new-onset diarrhea, should be tested. 
  • Testing is performed on stool using one of the following methods approaches: 
    • Combination testing for detection of C. difficile antigen (glutamate dehydrogenase – GDH) and C. difficile toxins A/B by enzyme immunoassay (EIA) 
    • Molecular detection of C. difficile Toxin B. 
  • Interpretation: 
    • The absence of antigen and toxin is not consistent with C. difficile infection 
    • The detection of only antigen indicates nontoxigenic C. difficile and can be consistent with a colonization state.  
  • The detection of toxin indicates a toxigenic strain of C. difficile and is consistent with C. difficile infection in a patient with the appropriate clinical symptoms. 

Note: At BJH, molecular testing is performed by reflex only if EIA detects positive antigen  and negative toxins A/B or results as invalid. It is also available by request for cases of high clinical suspicion. 

Common Pitfalls
  • Asymptomatic colonization with C. difficile is common in children and patients with risk factors including recent hospitalization and acid-suppressive medications. 
  • Inappropriate C. difficile testing can lead to misdiagnosis, unnecessary antimicrobial treatment and increased healthcare costs. 
Key Takeaways
  • C. difficile testing is NOT recommended from asymptomatic individuals. 
  • Testing is not recommended for individuals receiving laxatives or infants (1-year-old or younger). 
  • Repeat testing is not recommended. If C. difficile testing is negative and there is a strong suspicion of infection, wait at least 96 hours before sending another specimen. 
  • Monitoring or testing to assess cure is not recommended.  
References
  1. Rao et al. JAMA. 2020. 14;323(14):1403-1404 
  2. Clinical Practice Guidelines for Clostridium difficile Infection in Adults and Children: 2017 Update by the Infectious Diseases Society of America (IDSA) and Society for Healthcare Epidemiology of America (SHEA). Clin Infect Dis. 2018 Mar;66(7):987-994.   

Written By: Patricia Hernandez, MD

Reviewed By: Melanie Yarbrough, PhD

Last Edited: 2023-08-30

Last Reviewed: 2023-08-30