A two-step algorithm for Clostridioides difficile infection testing may reduce the need for GI consults and unnecessary treatment and improve detection, according to data presented at ECCMID 2023: the European Congress of Clinical Microbiology & Infectious Diseases (abstract E0231).

A multistep algorithm is recommended by current guidelines to increase specificity and sensitivity when testing for CDI, so researchers sought to evaluate results when switching from a two-step to a one-step workflow for C. difficile testing on CDI treatment in a large community-setting health system.

“Clostridioides difficile, or C. diff infection, is a significant burden for both the healthcare system, because of our increased expenditures, as well as for the patients—from increased mortality increased morbidity standpoint. And we do know that guidelines recommend a multistep approach for C. diff testing compared to utilizing a single step alone,” said study researcher Olivia Knack, PharmD, a PGY-1 clinical pharmacist at AMITA Health Saint Mary and Elizabeth Medical Center, in Chicago.

The researchers retrospectively assessed the transition of multiple centers from a one-step (polymerase chain reaction [PCR]) to a two-step algorithm (PCR plus toxin A/B reflex) for the evaluation of CDI. The pre-implementation period was from Nov. 20, 2020, to May 6, 2021, and the post-implementation period spanned from July 2 to Dec. 26, 2021. Receipt of stool softeners/laxatives within 48 hours of testing, selected concomitant medications, and CDI diagnosis or prophylaxis prior to admission were included in the exclusion criteria.

The frequency of CDI treatment initiation was the study’s primary outcome. CDI positivity type, CDI antibiotic days, all-cause in-hospital mortality, length of stay (LOS) in days, frequency of infectious diseases and gastroenterology consults, and antimicrobial stewardship program (ASP) interventions were included as secondary outcomes.

The researchers used the chi-squared test to analyze categorical data, and significance was defined as a P value less than 0.05.

Each of the study arms included 155 patients. The researchers reported CDI treatment initiation was higher in the one-step compared with the two-step group (n=154 [99%] vs. n=122 [79%]; P<0.0001, respectively). They observed detection of community-associated CDI (CA-CDI) and hospital-onset CDI (HO-CDI) was lower in the two-step group compared with the one-step arm (CA-CDI: n=14 [9%] vs. n=2 (1%); P=0.002, respectively; HO-CDI: n=37 [24%] vs. 11 [7%]; P<0.0001, respectively).

“In terms of our primary outcomes, really what we were looking at is the frequency of CDI treatment initiation, which was about 100% of the time, actually 99%, in our one-step method compared to 79% in our two-step method. So you can see here that there was a decrease in the two-step method compared to the one-step method,” Dr. Knack said. “And we’re thinking this is likely due to more of a highlight on the toxin results, but also possibly because antimicrobial stewardship intervention, which we did see did go up compared from the one-step to the two-step group. So, more [ASP] intervention can potentially really drive optimal diagnosis from a diagnostics standpoint.”

Compared with the one-step group, CDI antibiotic days were lower in the two-step arm for inaptients and outpatients (836 vs. 639; and 1,098 vs. 741, respectively).

The researchers reported all-cause in-hospital mortality was similar between the one- and two-step arms of the study (n=14 [9%] vs. n=9 [6%]; P=0.27, respectively), as well as median LOS (5 [range, 0-738] vs. 5 [range, 0-76]) and frequency of an ID consult (103 [66%] vs. 104 [67%]).

The number of gastroenterology consults was lower with the two-step algorithm (74 [48%] vs. 93 [60%]) and ASP intervention was higher (62 [40%] vs. 30 [19%]).

The researchers concluded that compared with a one-step algorithm, a two-step method reduced unnecessary treatment, improved CDI detection and reduced the incidence of reportable HO-CDI.

—GEN Staff

A version of this article first appeared in our sister publication Infectious Disease Special Edition