UC San Diego

Background: It is clinically important to distinguish C.difficile colonization from active infection, yet diagnostic methods are not standardized.. A two-step algorithm test is recommended to improve the accuracy CDI detection compared to traditional one-step testing, but clinical assessment and decision to treat CDI continues to vary across clinical settings.

Objective: Understand the impact of the transition from a one-step to a two-step method for CDI on diagnostic accuracy, treatment decisions, patient outcomes and reporting.

Methods: Two UC San Diego Health (UCSDH) in-patient populations were studied. In Phase 1 (July 1st, 2022, to August 31st, 2023), the two-step method with reflex toxin EIA testing was piloted in the Hematology-Oncology unit and 44 Polymerase Chain Reaction positive (PCR+) patients underwent toxin Enzyme Immunoassay (EIA) testing. In Phase 2 (December 1st, 2023, to April 30th, 2024), the two-step method was implemented house-wide and 157 PCR+ patients were tested for the toxin. Patient charts were reviewed using EPIC to collect data on patient demographics, isolation precautions, treatment, CDI complications, mortality and isolation costs. Statistical analyses were used to compare the outcomes of PCR+EIA- (colonized) to the PCR+EIA+ (active infection) patients in Phase 2 compared to Phase 1.

Results: In Phase 1, the duration of isolation in the colonized group (8.53 days) was similar to that of the active infection group (8.75 days). In addition, duration of CDI antibiotics was not statistically different in the colonized vs. active infection group: 11.5 vs. 11.1 days. In Phase 2, providers discontinued CDI precautions in the colonized compared with the active infection group, leading to reduced isolation days: 1.92 vs 8.98 days. Treatment was given only to 9 (12%) colonized compared to all 86 with active infection.

Conclusion: The implementation of the two-step method resulted in a change in provider behavior leading to a reduction of CDI precaution orders, treatments and cost in Phase 2.

Keywords: CDI, C.difficile, Colonization, Two-step diagnostic method, Antibiotic Stewardship