How to Prevent C difficile Infection: A New Guide

Laura A. Stokowski, RN, MS


May 24, 2013

In This Article

CDI: Making the Diagnosis

CDI is a toxin-mediated disease, which is the basis of the available diagnostic tests for CDI. The most widely used diagnostic test is enzyme immunoassay (EIA) for toxins A and B because these tests are relatively inexpensive, easy to perform, and have a rapid turnaround time.[6] Their poor sensitivity, however, can result in repeat testing and overtreatment. More sensitive methods, such as toxigenic stool culture, cell cytotoxicity, and glutamate dehydrogenase testing, are more expensive, slower, or more complicated to perform, limiting their clinical usefulness. The guide does not advocate for a particular testing strategy.

The future of diagnostic testing for CDI, according to Dr. Limbago, is in molecular methods, such as polymerase chain reaction (PCR), used either alone or in combination with EIA in multistep testing. "Regardless of which test you use," cautioned Dr. Limbago, "you must understand the limitations of the test, and how your results might change with a different test." For example, if a hospital is tracking its CDI rate using EIA but switches to PCR, the higher sensitivity of PCR can lead to the erroneous conclusion that the CDI rate has increased.

Dr. Limbago also emphasized the importance of testing only symptomatic patients. In other words, patients who are tested must be having diarrhea, defined as 3 or more unformed stools (stool that takes the shape of the container that it is placed in) in 24 hours. Laboratories should reject samples of formed stool sent for C difficile testing.

Inappropriate testing strategies can result in the identification and treatment of asymptomatic carriers. Evidence suggests that if clinicians look for C difficile, they will find it, because 10% of hospitalized patients are asymptomatic carriers,[4] although they do not require testing, isolation, or treatment.

Surveillance. The APIC guide defines surveillance as "the ongoing, systematic collection, analysis, interpretation, and dissemination of data regarding a health-related event to reduce morbidity and mortality and to improve health." With respect to CDI, surveillance requires the consistent use of a case definition for CDI, identification of the patient population at risk, calculation of CDI rates, and use of control charts to demonstrate trends and provide feedback to all stakeholders in the prevention of CDI. Interventions should be linked to surveillance results.[2]

Tracking a facility's CDI rate is no longer optional. In January 2013, the Centers for Medicare & Medicaid Services Inpatient Prospective Payment System began to require reporting of laboratory-identified CDIs through the National Health Safety Network (NHSN).[7] This will be a new responsibility for many healthcare facilities. The Pace of Progress Survey recently found that before reporting was required, only 27% of healthcare facilities voluntarily reported their CDI rates.


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