Empowering Lab Efficiency with Integrated C. diff Testing Model

Empowering Lab Efficiency with Integrated C. diff Testing Model

Article highlights:

  • Nearly 500,000 people in the United States are infected with C. difficile each year.

  • The Roche cobas® 4800 System offers batch testing and same-day results.

Diagnosing Clostridium difficile infection (CDI) can be a challenge for many healthcare organizations and requires specific testing protocols. Because laboratory testing by PCR for the spore-forming bacterium cannot discern the difference between CDI and colonization, facilities must take care to avoid false-positive results that might lead them to treat patients unnecessarily. Hospitals usually minimize this risk, which must be balanced with the need for timely treatment in positive cases, by only testing patients who have clinically significant diarrhea. Those who test positive are typically prescribed antibiotics, and are kept in isolation until their symptoms resolve.

Even with the high threshold for initiating testing (diarrhea three or more times over 24 hours without the use of laxatives), many laboratories face constant demand for their C. difficile-related services. The U.S. Centers for Disease Control and Prevention has estimated that around 500,000 people in the United States are infected with C. difficile each year.1 A typical lab might run thousands of C. difficile tests annually, all under pressure to do so cost-effectively and to deliver quick and accurate results.

Case Study: HealthPartners and Regions Hospital Laboratory


How any given provider handles C. difficile testing will depend on its laboratory resources, but the strategy employed by one health system in particular stands out for its ability to support the organization's financial and quality goals.

In a recent Medical Laboratory Observer (MLO) article,2 Nicole Zitterkopf Khoury, PhD, D(ABMM), MPH, MT(ASCP), laboratory scientific and accreditation director at HealthPartners and Park Nicollet Medical Groups, explains how HealthPartners—an integrated, nonprofit provider in Minnesota with six hospitals and approximately 100 satellite clinics—conducts all outpatient C. difficile testing in just one of its hospital laboratories. In 2016, Khoury reports, HealthPartners' Regions Hospital laboratory in St. Paul performed nearly 7,500 tests for C. difficile. About a quarter of those tests were for inpatients, while the rest were for outpatients from the satellite clinics.

CDI testing for outpatients was centralized in 2016, while hospital inpatient testing remained onsite, within each hospital-based laboratory. Khoury and her colleagues implemented this testing strategy based on three overarching goals: to help the organization "deliver quality care," to "create a positive experience for the patient and healthcare team," and to “maintain cost-effective testing" across their health system.


Getting There: Optimizing Testing Resources


Before determining that consolidation was the answer, they first defined their needs around inpatient and outpatient testing, Khoury writes. On the inpatient side, for example, they knew they required three specific things: a "sensitive, specific assay with a reliable negative predictive value"; a turnaround time (TAT) of less than one hour "to promote patient care and reduce transmissions"; and an assay that was easy to use, so they wouldn't have to invest in extensive staffing and training. For outpatient testing, on the other hand, they'd also require an "easy-to-use" assay with high sensitivity and specificity, but same-day TAT would suffice.

A system providing very rapid turnaround time was needed for lower volume inpatient sample testing. However, high volume outpatient testing would benefit from a batch- based system run once per day. Khoury and her colleagues realized they had the solution already in place at the Regions Hospital laboratory. The outpatient C. diff testing could be performed on the same analyzer utilized to test for human papillomavirus by polymerase chain reaction (PCR). They could add C. diff to the system's testing menu, and it would allow them to run up to 96 tests at a time with highly sensitive and specific performance per hospital requirements. (The cobas® Cdiff Test identifies the toxin B gene found in toxigenic C. difficile strains and minimizes the risk of false-negative results through its broad coverage of more than 30 toxinotypes and 20 ribotypes.) This batch-testing functionality would be well-suited for tests that didn't require on-demand results, and because staff were already familiar with the device, very little additional training would be necessary. "No additional capital acquisition was required," she writes. The solution, the Roche cobas® 4800 system, would be a "cost-effective method to consolidate outpatient C. difficile testing."

Looking Ahead: Meeting the Ongoing C. difficile Challenge


As the team at HealthPartners can certainly attest, PCR testing on its own will never be enough to stop C. difficile. Rather, the C. diff solution inevitably requires constant collaboration across the healthcare enterprise, from the physicians and nurses working face-to-face with patients, to the microbiologists scouring samples in the lab. Organizations should have policies and procedures in place to identify CDI hotspots in their facilities and minimize the spread of infection to other areas. And finally, they should understand PCR testing itself: that tests should be conducted only on those patients who exhibit CDI symptoms, and that proper specimen collection and handling are required for accurate results.

In the current world of "value-based care," where providers are rewarded for care quality and controlling costs, most organizations can't afford to be misdiagnosing C. difficile. Additionally, medical labs providing these critical test results face staffing challenges, budget cuts, and pressure to perform more efficiently without sacrificing quality or delivery time. HealthPartners' two-pronged C. difficile testing strategy helped address these challenges and prepare the lab for growth. According to Dr. Khoury, "We are now able to support growth in C. difficile testing without adding additional team members to the testing area or instrumentation...and have successfully re-allocated employees to other areas requiring more hands-on time." She goes on to say, "Provider satisfaction is still very high, and we are pleased to offer this testing solution to support the care of our system's C. difficile patients."


  1. CDC. Clostridium difficile Infection. March 2016.
  2. Khoury N. Optimizing C. difficile testing in a large system lab by integrating inpatient and outpatient needs. Med Lab Obs. 2017; 49(10): 37-38.

Contributing Lab Leader

Nicole Zitterkopf Khoury

VP Laboratory Service Line



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