Two-Step Algorithm Helps Reduce C Difficile Infection Antibiotic Use

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Patients who were PCR positive or likely colonized in the two-step era were 20 times less likely to be associated with treatment for CDI, without adversely impacting patient outcomes.

By implementing a testing program that involves both toxin and PCR tests, investigators proved the ability to detect and diagnose clostridiodes difficile infections (CDI), while reducing antibiotic use.1

A team, led by Lana Dbeibo, MD, identified the association between changing CDI diagnostic methods and the way testing results are displayed and the rates of CDI-specific treatment.

The Challenges in Diagosing CDI

It is often difficult to diagnose CDI, mainly due to high colonization rates. While PCR testing is commonly used, there are some flaws and limitations. On the other hand, a two-step algorithm platform that includes both toxin and PCR tests, could help differentiate colonization from active infection.

The current drawback is it is not currently known whether this type of testing impacts treatment decisions.

In the retrospective study, the investigators examined 610 C. difficile cares over a 2 year time period that spanned the year preceding and following the institution’s transition from PCR to two-step testing.

Comparing the Tests

During the PCR period, the CDI diagnostic results were displayed in the electronic medical record as “positive”, while the results in the PCR period were displayed as “likely colonized” or “toxin positive.”

The team compared the rates of CDI-specific therapy and adverse patient outcomes, including 30-day mortality and intensive care unit admission, between the 3 groups.

The results show 93% (n = 329) of patients in the PCR group were treated with CDI-specific therapy, while 42% (n = 59) in the likely colonized group were treated and all 114 patients in the toxin positive group were treated.

After conducting a multivariate analysis, the investigators found patients who were PCR positive or likely colonized in the two-step era were 20 times less likely to be associated with treatment for CDI, without adversely impacting patient outcomes.

“We found a correlation between changing the type of test and the way the results were displayed, and reduction in CDI-specific antibiotic use without restricting clinician diagnostic ordering,” the authors wrote. “This strategy may warrant consideration in other conditions where antibiotics are overprescribed, such as urinary tract infections.”

Rapid Near Patient Testing

Another method to reduce the burden of CDI is by using rapid near patient testing programs around suspected CDI cases in hospital settings, which could result in a number of positive patient outcomes.

Generally, when there are suspected cases of CDI in hospital settings, the reaction is patient isolation, laboratory testing, infection control, and presumptive treatment.

In the two-period pragmatic cluster randomized crossover trial, the investigators examined patients at 39 wards and divided them into 2 separate arms.

The results show a significant decrease in patient isolation time for the NPT group compared to the others (NE 9.4 hours; <0.01, ITT, 2.3; <0.05; PP, 6.7; <0.1), as well as a significant reduction in hospital length of stay for short stays (NE, 47.4%; <0.01; ITT, 18.4%; <0.01; ITT, 34.2%; <0.01).

Every additional hour of delay for a negative result resulted in an increase in metronidazole use (24 DDD per 1000 patients; <0.05) and non-CDI treating antibiotics by 70.13 mg (<0.01).

NPT testing saved $25.48 per patient including test cost and patient isolation.


Dbeibo, L., Lucky, C. W., Fadel, W. F., Sadowski, J., Beeler, C., Kelley, K., Williams, J., Webb, D., & Kara, A. (2023). Two-step algorithm-based Clostridioides difficile testing as a tool for antibiotic stewardship. Clinical Microbiology and Infection.