Nucleic Acid Amplification Test Quantitation as Predictor of Toxin Presence in Clostridium difficile Infection

Area of Science:

• Clinical Microbiology
• Infectious Diseases
• Diagnostic Technology

Background:

• Multistep algorithmic testing using nucleic acid amplification test (NAAT) followed by enzyme immunoassay (EIA) is accurate for diagnosing Clostridium difficile infection (CDI).
• This approach requires multiple tests, potentially delaying treatment for CDI.
• There is a need for faster preliminary diagnostic methods for CDI.

Purpose of the Study:

• To evaluate if quantitative results from the initial NAAT in a two-step algorithm can predict CDI toxin status.
• To assess the potential for preliminary CDI diagnosis based on organism burden measured by NAAT quantification cycle (C) values.

Main Methods:

• Retrospective analysis of 4,387 samples from two Dutch hospitals undergoing CDI testing.
• Utilized a two-step algorithm: NAAT followed by toxin A/B EIA.
• Analyzed mean C values from NAAT-positive samples in relation to subsequent toxin EIA results.

Main Results:

• Significantly lower mean C values were observed in NAAT-positive samples that eventually tested positive for toxin compared to those testing negative (P < 0.001).
• Receiver operating characteristic curve analysis showed high predictive ability for C values (AUCs of 0.826 and 0.854).
• Optimal C cutoff values accurately predicted eventual toxin EIA results for 78.9% and 80.5% of samples.

Conclusions:

• Quantification cycle (C) values from NAAT can serve as predictors of toxin status in CDI testing.
• While C values offer predictive insights, they do not fully replace the need for confirmatory toxin testing due to suboptimal correlation.
• Further toxin testing is still required for definitive CDI diagnosis.