Clinical outcomes of toxin-positive versus toxin-negative/NAAT-positive Clostridioides difficile infection in South Korea: a single-center retrospective cohort study.

BACKGROUND

Current guidelines recommend multistep algorithms incorporating nucleic acid amplification tests (NAATs) and toxin enzyme immunoassays (EIAs) for the diagnosis of Clostridioides difficile infection (CDI); however, the clinical significance of toxin-negative/NAAT-positive (toxin-/NAAT+) results remains uncertain. We aimed to compare clinical outcomes between toxin + and toxin-/NAAT+ cases.

METHODS

This retrospective study included adults diagnosed with CDI between September 2020 and September 2025 at a tertiary hospital in South Korea. Patients were classified by toxin EIA and NAAT results into toxin + or toxin-/NAAT+ groups, and their outcomes were compared. The primary outcome was CDI recurrence within 90 days. Secondary outcomes included 60-day recurrence, 90-day all-cause mortality, resolution of diarrhea, and colectomy for CDI.

RESULTS

In total, 382 toxin + and 435 toxin-/NAAT+ were evaluated. CDI recurred in 55 patients (6.7%), including 35 (9.2%) in the toxin+ group and 20 (4.6%) in the toxin-/NAAT+ group (P = 0.011). Toxin positivity was significantly associated with recurrence (adjusted odds ratio [aOR], 1.99; 95% confidence interval [CI], 1.12-3.52; P = 0.019). Prior antibiotic exposure was also associated with recurrence (aOR, 2.24; 95% CI, 1.25-4.02; P = 0.007). Toxin positivity was not associated with 90-day mortality (aOR, 1.19; 95% CI, 0.85-1.69; P = 0.313).

CONCLUSIONS

In our cohort, toxin positivity was associated with an increased risk of 90-day recurrence but not with 90-day mortality. Our data indicate that incorporation of toxin EIA testing into CDI diagnostic algorithms could provide clinically relevant prognostic information.

TRIAL REGISTRATION: Not applicable.