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Description

Clostridioides difficile is a Gram-positive obligate anaerobe long associated with healthcare-acquired infections in the United States. 1 Clostridioides difficile infection (CDI) has thus become a key metric for assessing facility cleanliness and iatrogenic infection. C. difficile carriage is common, present in approximately 8% of hospitalized patients.2 Therefore, appropriate patient selection for testing and careful testing procedures is crucial to appropriately identify CDI while avoiding the detection of chronic colonization.

Considerable variability exists among institutions regarding standardized CDI laboratory diagnostic methods. Historically, the gold standard for CDI testing was the clinically inefficient toxigenic culture (TC). 3 This was followed by cytotoxic assays (CTA) and then enzymelinked immunoassays (EIA), which directly tests for the bacterial toxin.4 However, EIA use alone was often deemed insufficient and required additional testing to improve sensitivity. 4 Testing for the isoenzyme glutamate dehydrogenase (GDH), specific to the Clostridioides species, can be added to EIA toxin testing to improve the sensitivity of the toxin testing result.5 However, GDH testing alone serves is a poor clinical indicator for CDI, as it does not differentiate those with active CDI vs those colonized with C. difficile, and has the potential to identify other close species.5 Combination toxin EIA and GDH testing improves both sensitivity and specificity for CDI, but can leave clinical uncertainty with incongruent results (ie. GDH+ Toxinpatients).

PCR testing exists as another option for CDI, and identifies Toxin A and Toxin B genes with high sensitivity and produces rapid results.4 While PCR identifies toxigenic C. difficile strains and eliminates those that are non-toxigenic, it fails to identify the active production of toxins. Since toxin production is correlated with active infection, PCR alone is unable to distinguish active infection from colonization.

Current CDI testing guidelines recommendation a multi-step approach that tests for C. difficile strains and active toxin production.1 This can be accomplished with GDH and toxin EIA or PCR and toxin EIA, with some algorithms reflexing to PCR in non-congruent GDH/EIA results. In November 2019, Beaumont Health changed its CDI testing policy to default to GDH and toxin EIA. While PCR remained available, testing could only be performed by consultation of and ordering by an infectious disease physician.

Publication Date

5-2025

Keywords

Clostridioides difficile

Disciplines

Infectious Disease

Comments

The Embark Capstone Colloquium at the Oakland University William Beaumont School of Medicine, Rochester Hills, MI, May, 2025.

Treatment Rates in a Two-Step Clostridioides difficile Diagnostic Testing Algorithm

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