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Single-Step NAAT Algorithm Improved C. difficile Detection

Issue: Premier Issue 2014

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WASHINGTON, D.C. — A single-step nucleic acid amplification test in combination with a strict stool rejection policy detected more cases of Clostridium difficile compared with a combination of enzyme immunoassays and toxigenic culture, according to data presented at ICAAC 2014.

Nathalie Jazmati, MD, University Hospital of Cologne, and colleagues prospectively tested 782 patient stool specimens for C. difficile infection (CDI) under routine conditions from November 2013 to February 2014. They used enzyme immunoassays (EIA), toxigenic culture (TC) and real-time polymerase chain reaction for the nucleic acid amplification test (NAAT) in combination with a stool rejection policy following international guidelines to avoid false positives. This policy involved rejection of a sample when stool was formed, tested repeatedly within 4 days after a negative result or 7 days after a positive result. Multiple tests of individuals also was avoided.

 

Nathalie Jazmati

Using the single-step NAAT algorithm resulted in fewer specimens screened (17%) and number of screened patients per month (228+/-30 vs. 244 +/-18, P=.33) and percentage of positive patients increased (11% +/- 4.1 vs 14 +/- 2.3, P=.20) but data were not significant. Of all specimens analyzed, 165 tested positive for CDI by NAAT, including 39% that could not be confirmed by TC and EIA. Among undetected CDI specimens by TC and EIA, 12 and 21 tested positive for TcdC-deletion (ribotype 027) and binary toxin, respectively. The retrospective review of the charts from patients with discrepant results showed that 94% of the 35 patients had a true CDI.

"Using NAAT as a single-step algorythm is highly sensitive," Jazmati told Healio.com/Gastroenterology. "If positive results are assessed carefully with clinical data single-step NAAT can serve as a new gold-standard in diagnosis of CDI."

For more information:

Jazmati N. Abstract D-201. Presented at: Interscience Conference on Antimicrobial Agents and Chemotherapy; Sept. 5-9, 2014; Washington, D.C.

Disclosure: The researchers report no relevant financial disclosures.