Diagnostic approaches to Clostridioides difficile infection

Diagnostic approaches to Clostridioides difficile infection

Approach	Description	Advantages	Disadvantages	Interpretation
Preferred approaches (two-tiered approach that includes an initial highly sensitive test followed by a highly specific test)
NAAT followed by toxin EIA test	NAAT (highly sensitive) is performed first, followed by the toxin EIA (highly specific) if the NAAT is positive	High sensitivity Helps distinguish between colonization and true infection	Toxin EIA can be falsely negative	+NAAT, +Toxin EIA: CDI +NAAT, –Toxin EIA: Asymptomatic carriage or CDI with falsely negative toxin EIA^* –NAAT: No CDI and no asymptomatic carriage
GDH antigen test followed by toxin EIA test	GDH (highly sensitive) is performed first, followed by toxin EIA (highly specific) if GDH is positive	High sensitivity	Toxin EIA could be a false negative	–GDH: No CDI +GDH, +Toxin EIA: CDI +GDH, –Toxin EIA: Asymptomatic carriage or CDI with falsely negative toxin EIA^*
GDH antigen and toxin EIA tests (followed by NAAT if discrepant results)	GDH and toxin EIA are both performed first, followed by NAAT if there is a discrepancy in GDH and toxin EIA results	High sensitivity Combination of all three tests increases specificity	Resource-intensive A positive NAAT test in the setting of discrepant GDH and Toxin EIA results still does not completely distinguish between true CDI and asymptomatic carriage.	+GDH, +Toxin EIA: CDI +GDH, –Toxin EIA, +NAAT: CDI or asymptomatic carriage^* +GDH, –Toxin EIA, –NAAT: No CDI and no asymptomatic carriage –GDH, +Toxin EIA: Technical error, repeat testing –GDH, –Toxin EIA: No CDI and no asymptomatic carriage
Alternative approaches
NAAT only	NAAT/PCR that detects toxin gene	High sensitivity Rapid results	Low specificity Cannot distinguish true infection from colonization	(+) NAAT: CDI or asymptomatic carriage^* (–) NAAT: No CDI and no asymptomatic carriage
GDH antigen test followed by NAAT	GDH is performed first, followed by the NAAT if GDH is positive	High sensitivity Rapid results Inexpensive	Low specificity Uses two tests with high sensitivity but both with low specificity Cannot distinguish true infection from colonization	+GDH, +NAAT: CDI or asymptomatic carriage* +GDH, –NAAT: No CDI and no asymptomatic carriage –GDH: No CDI and no asymptomatic carriage

This table outlines the different diagnostic approaches available for the diagnosis of CDI. Approach to testing is often determined by an institution's microbiology lab protocol and is not a decision needed to be made by the clinician.

CDI: Clostridioides difficile infection; EIA: enzyme immunoassay; GDH: glutamate dehydrogenase enzyme; NAAT: nucleic acid amplification test; PCR: polymerase chain reaction.

* In cases where the results are discordant, the clinician must evaluate the clinical presentation of the patient to determine whether the patient likely has CDI or if the symptoms are more likely due to another cause. Refer to the topic on diagnosis of CDI for more detailed information on how to interpret discordant results.

Graphic 146041 Version 2.0

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Diagnostic approaches to Clostridioides difficile infection