# Impact of switching from polymerase chain reaction-only to two-step Clostridioides difficile testing in a large hospital system

## TL;DR

Switching to a two-step testing method for C. difficile infection in a hospital system reduced ICU transfers and readmissions without harming patient outcomes.

## Contribution

This study evaluates the clinical impact of adopting a two-step CDI testing algorithm in a large hospital system.

## Key findings

- In moderate-risk patients, two-step testing reduced ICU transfers and readmissions by 5% and 7%, respectively.
- Anti-CDI antibiotics were discontinued in 15% of EIA-negative patients using the two-step method.
- No significant differences in other complications were observed between testing groups.

## Abstract

Clostridioides difficile is the primary cause of healthcare-associated infectious diarrhea in hospitalized patients. The most common laboratory testing methods for C. difficile infection (CDI) are toxin detection via enzyme immunoassay (EIA) and polymerase chain reaction (PCR), which detect a toxogenic strain. This study examines the impact of Rhode Island’s largest hospital system changing from PCR-only to two-step CDI testing.

A retrospective cohort study of 2,173 adult inpatients was conducted. Patients were grouped into two cohorts: those tested for toxigenic C. difficile via PCR-only (June 2019–May 2021, n = 1,194) and those tested with the two-step algorithm (June 2021–May 2023, n = 979). Cluster analysis identified patient risk groups for hypothesis generation, and complications such as death, colectomy, intensive care unit ICU transfer, and 30-day readmission were compared across these groups.

In the moderate-risk group, there was a significant reduction in ICU transfers and readmission rates with the two-step testing by 5% and 7%, respectively. There were no other significant differences in complications between testing groups. Anti-CDI antibiotics were discontinued in 15% (n = 106) of EIA-negative patients in the two-step testing group. Moderate-risk patients were less likely to have treatment discontinued than severe-risk patients (OR = 2.00, p = 0.016).

The two-step testing algorithm did not negatively affect patient outcomes and led to a modest decrease in anti-CDI treatment, supporting the safety of two-step CDI testing in hospitalized patients.