Reducing C. difficile: Why Testing Stewardship Usually Comes First
Among hospitals working to lower their Total HAC Score, C. difficile is frequently the largest single contributor. Yet the quickest measurable gains usually do not result from more aggressive cleaning. They come from a clear understanding of which patients are tested, and the way testing is done.
That can be an uncomfortable recommendation to make, since it can sound like gaming the measure and attempting to manipulate the metrics. It is not. Most hospitals are detecting organisms in patients who don't have the disease, treating some of them, and reporting all of them.
Why is C. diff so often the top score driver?
CDI is reported through NHSN as a laboratory-identified event, so its structural is different from CLABSI or SSI data collection and reporting.
There's no clinical case review or adjudication. If a stool specimen collected on day 4 admission or later, it is classified as a healthcare-facility-onset event. No infection preventionist reads the chart and decides whether the patient actually had the disease.
As a result, the rate you report is determined directly by your laboratory's testing volume and approach.
NHSN states this plainly: because PCR is highly sensitive, it can cause a facility to identify more CDI events which, in turn, results in a higher SIR. Although the risk adjustment accounts for test type, it cannot account for how many inappropriate specimens your lab receives.
What does a positive test actually mean?
A meaningful proportion of healthy adults and a substantially higher proportion of hospitalized patients carry C. difficile bacteria without active disease. A NAAT identified the gene responsible for toxin production — that is, the organism's ability to cause illness, not evidence that it is actively doing so.
So if a patient has diarrhea caused by a laxative, tube feeding, or chemotherapy, a positive result only tells you the organism is present. It does not tell you it's the source of the illness.
This is why current recommendations are framed the way they are. Testing is ideally reserved for patients with unexplained, recent-onset diarrhea, defined as three or more unformed stools within 24 hours. Laboratories are told to refuse samples that are not liquid or soft — if a specimen keeps its form, it should not be analyzed. Repeating tests and ordering tests of cure are both discouraged, since results may stay positive for six weeks or more after treatment has worked.
What does diagnostic stewardship look like in practice?
Four interventions, roughly in order of impact:
Rethink the testing workflow. A two-stage approach — first a sensitive NAAT or GDH, then a toxin assay with high specificity — distinguishes colonization from probable infection much better than NAAT by itself. For most hospitals, this is the biggest gain available, and it is carried out entirely in the lab.
Require the criteria at the point of ordering. Before the request can move forward, there should be documentation of three or more unformed stools within 24 hours and no laxative use in the previous 48 hours.
Empower the laboratory to reject inappropriate specimens. If a sample does not match the container requirements, the lab should turn it away. This must be written as policy, not left to discretion, or it will not hold up during a hectic overnight shift.
Eliminate repeat testing and tests done for cure. Both create positive results that have no clinical meaning, yet still count against you in full.
One caution worth taking seriously. The advice to not re-test within 48 hours of a laxative is a relatively weak recommendation based on low-quality evidence, and a later study of patients with confirmed CDI found no difference in illness severity between those who had taken laxatives and those who had not. Using a laxative does not exclude infection.
Hard stops that cancel orders without notice can do real damage: a care team may wait for days for a result that was never going to be produced. Provide an override route, ensure cancellations are visible to the clinician who ordered the test, and treat the criteria as guidance to consider rather than an absolute barrier.
Antibiotic stewardship and CDI reduction are the same project
Antibiotic use is the main modifiable risk factor for CDI. A patient who never receives an unneeded antibiotic is a patient whose microbiome was never disrupted.
When your infection prevention program and your stewardship program report through different committees on different scheduled, you effectively have two projects addressing the same problem. The CDI reduction effort that endures is usually the one where the work of those two groups were brought together.
Where environmental controls fit
C. difficile spores can persist on surfaces for months, and they withstand routine quaternary ammonium disinfectants. Therefore, sporicidal agents are required for disinfection.
In most facilities, the problem is not product itself. Rather it is often contact time: the surface must remain visibly wet for the entire dwell period specified on the label, and in real world use it often does not. Monitoring that can often be more useful than switching products.
The environment also matters with C.difficile infection reduction. It simply tends to change the number more slowly than the laboratory or diagnostic stewardship changes do.
Where to start
If CDI is your largest HACRP score contributor, the useful first question and perhaps most useful may not be how to stop additional cases. Instead, ask where your current cases are originating: how many were tested from appropriate specimens, how many were repeat or cure tests, and what your positivity rate is relative to your testing volume.
IP&MA reviews CDI testing practice, prevention bundle implementation, and the surveillance data underneath your reported rate, then works with your team on the interventions most likely to move your score in the window that's still open.
Request a discovery call to talk through where your CDI cases are actually coming from and where you may have opportunity to improve.