Updated C diff Diagnostic Guidelines Released by ESCMID

The European Society of Clinical Microbiology and Infectious Diseases (ESCMID) has just released new guidelines on best practice methods to diagnose Clostridium difficile infection (CDI) (Clinical Microbiology and Infection).

“The new guidelines are intended for use among medical microbiologists, gastroenterologists, infectious disease specialists, and infection control practitioners,” explains professor Ed Kuijper, MD, Leiden University Medical Center (The Netherlands), whose research group has published the guidelines. “Our aim is to not only improve diagnosis of CDI, but also to standardize the diagnostic process…to allow for improved surveillance of the disease.”

Despite the development of new tests for CDI, the authors strongly recommend against the routine use of any single test, irrespective of the technology on which it is based. The new guidelines also make recommendations on repeated testing for both positive and negative samples, as well as on the selection of samples to be tested.

The following are the strongest recommendations based on the evidence:

• Samples to be tested for CDI should not be limited to cases in which a physician has specifically recommended a test.
• A rectal swab can be used for testing by toxigenic culture (TC), NAAT, or glutamate dehydrogenase (GDH) enzyme immunoassays (EIA) tests in patients with apparent ileus (inactive bowel with no discernable bowel sounds).
• Single, standalone tests are not reliable and should not be used: a two-step algorithm is necessary.

This two-step algorithm involves a combination of fast assays with follow up tests:

• Route one—the two-stage procedure should begin with either an NAAT or GDH EIA test. Negative tests should be treated as CDI negative, while positive tests should be followed up with a toxin A/B EIA test to confirm the result.
• Route two—the two-stage procedure should begin with both the GDH EIA test and the toxin A/B EIA test. If both are positive, CDI is likely to be present. If both are negative, CDI is unlikely to be present, however, if GDH is positive and toxin A/B is negative, then the tests may optionally be followed up with an NAAT or TC test.

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In endemic situations, repeat testing is not recommended after a positive result has been obtained but is advised after an initial negative sample from a patient with persistent, high clinical suspicion.

The new guidelines replace the original 2009 guidelines by the Society and are based on a met-analysis initiated in June 2014 of all relevant studies. The primary aim was to evaluate the diagnostic accuracy of commercially available lab tests in diagnosing CDI and to make recommendations for standard testing algorithms. —Amanda Del Signore