Clinical Impact of Clostridium difficile PCR Cycle Threshold-Predicted Toxin Reporting in Pediatric Patients

Background: Reliance on tests that detect only the presence of toxigenic Clostridium difficile can result in overdiagnosis and overtreatment of C difficile infection (CDI). The C difficile polymerase chain reaction (PCR) cycle threshold (CT) can sensitively predict the presence of free C difficile toxins; however, the clinical application for this testing strategy remains unexplored. We evaluated the impact of dual PCR and toxin result reporting, as predicted by the CT, on CDI management and outcomes in children.

Methods: Before the intervention, results for C difficile testing at Lucile Packard Children's Hospital Stanford were reported as PCR positive (PCR+) or negative (PCR-) according to the GeneXpert C diff Epi tcdB PCR assay (Cepheid, Sunnyvale, California). Beginning October 5, 2016, the presence of free toxins, as predicted by the CT, was reported also. The CDI treatment rates 1 year before and 18 months after implementation of toxin reporting were compared. Demographic and treatment-related data were collected, and patient outcomes were followed up 8 weeks later.

Results: CDI treatment decreased 22% after the intervention (96% [preintervention] vs 74% [postintervention]; P < .001). During the postintervention period, there were 152 PCR+C difficile results, and 94 (62%) of them were toxin positive (toxin+) according to the CT. Of the 58 PCR+/toxin-negative (toxin-) results, 38 (66%) did not result in CDI treatment. Seven (18%) of the untreated PCR+/toxin- patients underwent repeat testing within 8 weeks, and 5 (13%) of them were subsequently PCR+/toxin+ and treated. No CDI-related complications were identified.

Conclusions: Addition of the CT-predicted C difficile toxin result to PCR reporting reduces the proportion of PCR+ children treated for CDI.