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June 23, 2023
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Two-step testing associated with decreased incidence of hospital-onset C. difficile

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Key takeaways:

  • Two-step testing was associated with a decrease in hospital-onset C. difficile infection.
  • Similar decreases were observed in utilization rates for oral vancomycin and fidaxomicin.

Two-step Clostridioides difficile testing was associated with decreased reported incidence of hospital-onset C. difficile infection and C. difficile-specific antibiotic use, researchers found.

“Two-step testing has made some clinicians nervous that they might miss or delay C. difficile diagnosis in patients who are nucleic acid amplification testing positive/toxin negative (colonized),” Nicholas A. Turner, MD, MHSc, assistant professor in the division of infectious diseases at Duke University Medical Center, told Healio.

Credit: Adobe Stock.
Two-step C. difficile testing was associated with decreased reported incidence of hospital-onset C. difficile infection and C. difficile-specific antibiotic use. Image: Adobe Stock.
Nicholas A. Turner

“While there have been several previous individual-level studies that were quite reassuring, two-step testing has been around long enough that we thought it was time to take a look at larger scale hospital level data.”

Turner and colleagues performed a longitudinal cohort study of 2,657,324 patient-days at eight regional hospitals between July 2017 and March 2022 to assess the impact two-step testing.

Overall, two-step testing was temporally associated with a level change in hospital-onset C. difficile infection (HO-CDI) incidence (incidence RR = 0.53; 95% CI, 0.48-0.6) but no significant trend change afterward. Complete antibiotic use data were available for seven of the nine sites included in the study, covering a total of 94,097 days of therapy (DOT) for oral vancomycin and 1,305 DOT for fidaxomicin before conversion to two-step testing. Researchers found a similar level decrease to HO-CDI incidence in utilization rates for oral vancomycin and fidaxomicin (utilization RR = 0.63; 95% CI, 0.58-0.7), and no significant level (RR = 1.16; 95% CI 0.93-1.43) or trend (RR = 0.85; 95% CI, 0.52-1.39) change in emergent colectomy rates.

The researchers also conducted a post-hoc sensitivity analysis assessing potential for confounding effects related to the pandemic because of the pandemic taking place around the same time as the change in testing. They determined that although the COVID-19 pandemic was not temporally associated with any significant changes in HO-CDI incidence, the potential for pandemic-related effects introduced “sufficient uncertainty” that the effect of two-step testing on HO-CDI incidence rates was partly mitigated (level change IRR = 0.68; 95% CI, 0.43-1.06).

Turner said that these data are overall “really reassuring,” and complement prior studies.

“The absence of any delayed increase in HO-CDI incidence suggests we're not just delaying diagnosis — we're probably doing a better job at properly diagnosing patients,” he said.