Discussion

We investigated the impact of increased diagnostic test stewardship on C. difficile testing at a university hospital. From 2014, numerous interventions aimed at enhanced infection prevention were implemented and monitored until performance at high fidelity was achieved. Nevertheless, C. difficile rates remained high; providers ordered an average of 300 tests per month, with many patients lacking signs or symptoms to indicate testing. Introducing a new C. difficile testing algorithm, a Cerner-based decision support system using interactive dialogue boxes, resulted in a significant reduction in test frequency, and statistically significant improvement in test fidelity. This intervention also impacted the incidence of reportable C. difficile events. Teaching hospitals may be at particular risk of overtesting and overdiagnosing C. difficile due to the wide adoption of NAAT testing and potentially excessive ordering practices of trainees. Other institutions have targeted this group in particular for education and incentives for testing stewardship, with promising outcomes.Reference Madden, Mesner and Cox ⁴

Our experience highlights the impact of testing volume as a driver of C. difficile rate. Test stewardship is distinct from “gaming” efforts because only tests that do not meet criteria are discouraged. Overdiagnosis of CDI has adverse effects on patient care similar to any false-positive result. Positive results require contact isolation and private room assignment, and employees are required to wear proper protective equipment. Retrospective chart review demonstrated that 195 C. difficile–positive patients who were treated with C. difficile–targeting antibiotics did not meeting testing criteria. Antibiotic therapy is not recommended for those colonized with C. difficile, and given the disruption of gut flora caused by therapy, it may predispose colonized patients to future CDI.Reference Dubberke and Burnham ^{3 ,} Reference Morgan, Malani and Diekema ⁵ Providers must understand that patients with positive PCR results may not need treatment if they do not meet clinical criteria for infection. As a result, increased clinical understanding and test guidance is necessary to decrease unnecessary testing and treatment. Audit of service-line adherence to test fidelity and feedback to hospital leadership for dissemination to providers supports the goal of test stewardship and quality patient care in tandem with provider education.

The strengths of this study are the inclusion of negative and positive PCR results in the chart review and the granularity of data collected by manual chart review by the infection prevention team. A significant limitation of this study is that the results are confined to a single academic medical center over a short evaluation period. Although the improvement in test fidelity and decrease in testing volume seemingly decreased NHSN reported rates, such results must be interpreted with caution given short time of follow-up to date and concurrent infection prevention initiatives. Nevertheless, ongoing infection prevention efforts targeting C. difficile pre-date the EMR-based decision support and were maintained at high fidelity throughout the EMR implementation.

As more healthcare centers embrace test stewardship, there are concerns about missed or late diagnoses of C. difficile. No provider was denied the ability to perform a C. difficile test. We acknowledge that there may be circumstances that necessitate a C. difficile test despite lack of documented criteria. We further acknowledge that with an emphasis on thoughtful testing, it is possible that patients with true CDI were missed. Potentially, these cases may be diagnosed later with more severe disease. However, a review of all colon surgeries yielded zero colectomies for CDI during the study period. The potential benefits of C. difficile test stewardship must be assessed against the potential harms of under-diagnosis. More studies are needed to define optimal diagnostic strategies for C. difficile.

Test stewardship driven by EMR-based decision support decreased the frequency of C. difficile testing, improved test fidelity, and decreased the number of patients potentially overtreated with antibiotics for C. difficile colonization. Additional studies are needed to optimize C. difficile testing strategies and to minimize the potential harms of C. difficile underdiagnosis.