Clinical impact of toxin detection in children with PCR-confirmed Clostridioides difficile infection

The diagnosis of Clostridioides difficile infection (CDI) in children is challenging due to high rates of asymptomatic colonization and the limited ability of available assays to differentiate colonization from true infection. The relative utility of polymerase chain reaction (PCR) versus stool toxin A/B detection by enzyme immunoassay (EIA) remains uncertain in pediatric practice. This study aimed to evaluate whether stool toxin A/B detection adds incremental clinical value among children with gastrointestinal multiplex PCR positivity for C. difficile toxin genes (tcdA/tcdB) by comparing risk factors, treatment decisions, and outcomes according to toxin status. This retrospective observational study included 103 pediatric patients (< 18 years) with PCR positive for C. difficile toxin genes (tcdA/tcdB) results at a tertiary children's hospital between October 2022 and April 2025. Patients were categorized into three groups: stool toxin A/B not evaluated, stool toxin A/B negative, and stool toxin A/B positive. Demographics, risk factors, clinical characteristics, laboratory findings, treatment decisions, and outcomes were compared across stool toxin A/B groups. Of the 103 patients, 26 (25.2%) had no stool toxin A/B, 63 (61.2%) were stool toxin A/B negative, and 14 (13.6%) were stool toxin A/B positive. More than half of the cohort (54.3%) received CDI treatment, with no significant difference in treatment initiation rates among stool toxin A/B groups. The risk factors-including underlying disease (e.g., malignancies, inflammatory bowel disease, and immunodeficiencies), recent hospitalization, antibiotic exposure, and proton pump inhibitor (PPI) or enteral tube use-were similarly distributed. Clinical severity, laboratory parameters, imaging findings, recurrence, complications (1.0%), ICU admission (4.9%), and mortality (3.9%) did not differ significantly between stool toxin A/B positive and negative patients. Although a statistically significant difference in diarrhea severity was observed across groups, this was driven by the toxin-not-evaluated group. Importantly, stool toxin A/B positivity did not correlate with clinical severity, underlying risk factors, laboratory abnormalities, or outcomes.

In this pediatric cohort, stool toxin A/B detection did not provide additional clinical value beyond PCR positivity for C. difficile toxin genes (tcdA/tcdB). PCR alone, when interpreted in the context of compatible symptoms and epidemiological risk factors, may be sufficient to guide treatment decisions for suspected pediatric CDI. Given the limited incremental value of stool toxin A/B testing, optimized diagnostic algorithms and further multicenter pediatric studies are warranted.

• Pediatric CDI diagnosis is complicated by high asymptomatic colonization; PCR for C. difficile toxin genes (tcdA/tcdB) is sensitive but cannot distinguish colonization from infection. • Stool toxin A/B EIAs are more specific but less sensitive, and guidelines often recommend multistep algorithms.

• In our cohort of pediatric patients with PCR positivity for C. difficile toxin genes (tcdA/tcdB), stool toxin A/B status was not associated with clinical severity, risk factors, laboratory findings, outcomes, or treatment initiation. • When clinical features are compatible, PCR positivity for C. difficile toxin genes (tcdA/tcdB) alone may be sufficient to guide treatment, with limited incremental value of stool toxin A/B testing.