# PCR Cycle Threshold–Guided Management of Pediatric Clostridioides difficile Infections

## TL;DR

Using PCR cycle thresholds helps better manage pediatric Clostridioides difficile infections and reduces unnecessary antibiotic use.

## Contribution

The study demonstrates that PCR cycle threshold-guided diagnostics improve diagnostic precision and reduce inappropriate treatment in pediatric C. difficile cases.

## Key findings

- The QIAstat-Dx assay achieved 100% sensitivity and negative predictive value for detecting free toxins.
- Excluding co-infected samples increased the assay's specificity to 97%.
- Ct-guided strategies led to a 51% reduction in treated patients compared to pre-intervention periods.

## Abstract

This follow-up study expands on our previous work demonstrating that a PCR cycle threshold (Ct)–guided diagnostic approach improves the management of pediatric Clostridioides difficile infection (CDI) and reduces unnecessary treatment of colonized children. We evaluated the performance of the Gastroenteritis PCR Panel by QIAstat-Dx as a standalone method in combination with the PCR cycle threshold (Ct) value in PCR-positive samples to predict the presence of free toxins. In addition, we evaluated the impact of reporting toxin production results based on PCR Ct value alongside a comment in our electronic medical record. The QIAstat-Dx assay achieved 100% sensitivity and negative predictive value (NPV), with a specificity of 69% and a positive predictive value (PPV) of 63%. When 16 false-positive samples that were co-infected with other enteropathogens were excluded, the specificity increased to 97%. We observed a significant decrease (51% vs. 68%) in the proportion of treated patients in this study compared to the pre-intervention period of our previous study (p = 0.04). In contrast, a minor, non-significant 5% increase (p = 0.60) was observed in this study compared with the post-intervention period (45% treated) from the previous study. These findings demonstrate that Ct-guided diagnostic strategies continue to enhance C. difficile diagnostic precision and help limit inappropriate antibiotic use in our pediatric population.