Hospital Modifies Testing for C difficile to Ascertain Actual Rate of Hospital-Acquired Infection


Hospital posits that testing for C diff in patients without symptoms inflates rate of hospital-acquired infection with cases of asymptomatic colonization.

One hospital has reduced its (reported) rate of hospital-acquired C difficile infection (CDI) by limiting testing for Clostridioides difficile to patients with symptoms or clinical presentation of an infection, albeit with possible cases of asymptomatic colonization remaining undetected.

Winston McCormick, MD, Division of Infectious Diseases, Alpert Medical School, Brown University, Providence, RI, and colleagues note that the Centers for Medicaid and Medicare mandate that all acute-care hospitals report CDI laboratory-identified events, as one benchmark metric in comparing hospital quality and outcomes.

They point out, however, that hospital acquired infection is based "strictly" on a positive stool specimen collected three days after hospital admission, "regardless of symptoms onset or clinical presentation."

"Given the high prevalence of C difficile colonization among hospitalized patients, testing should primarily be considered in patients with at least 3 unformed stools within 24 hours, without recent laxative use," McCormick and colleagues argue.

With the apparent rate of hospital-acquired CDI at the 129-bed Newport Hospital, an affiliate of the medical school at Brown University, remaining above target despite an array of infection control measures, McCormick and colleagues decided to change the testing protocol for C difficile. The infection control measures had included electronic alerts, rejection of stool samples with inadequate consistency, and "soft-stop" orders.

Commencing July, 2019, an order for CD-NAAT test of stool sample collected after day 3 of hospitalization required an approval by infection control before being processed by the laboratory. Requests were submitted via the chat function of the electronic medical record, or via pager after hours and weekends.

"Approval was based on patient-focused discussions regarding testing necessity, considering number of loose stools, duration of symptoms, laxative use, antibiotic use, previous CD testing, and likelihood of other diarrheal causes," McCormick and colleagues explain.

In the first month after requiring approval before testing could be performed, the baseline of 13 tests per month was reduced to 6.The reported rate of hospital-acquired CDI decreased by 1.16 cases per 1,000 patient days (95% CI, -1.99 to -0.33).

The investigators reported that approved patients were 4 times as likely to have ≥3 loose stools in 24 hours. They also found that, although not statistically significant, the approved patients were 28% more likely to have had antibiotics in the past 7 days and 17% less likely to have a prior history of C difficile.

The investigators also determined that the 7 patients for whom testing was not approved had no increased mortality or longer hospitalization, or repeated requests for testing, "suggesting appropriateness of clinical decision guidance."

McCormick and colleagues calculated that the days of treatment with oral vancomycin and fidaxomicin per 1000 patient days declined from 23.7 before the change in testing protocol to 16.2. That there was no increase in days of treatment following the intervention suggested to the investigators that empiric treatments were not started to avoid the approval process.

"Direct interactions with staff were opportunities to explore alternative causes of diarrhea, confront testing drivers, and avoid duplicate and retesting after recent negative results," McCormick and colleagues indicated.

McCormick elaborated on the importance of a valid test for infection, in discussion with Contagion. "C diff infection is a major issue...and, as with any infectious disease, having high quality methods to categorize and identify types of infection—eg, community acquired, hospital acquired, infections vs colonization, etc—are critical in containing outbreaks and allocating resources appropriately," he commented.

McCormick explained that the new testing parameters more effectively identify cases of infection by passing over possible cases of asymptomatic colonization. "Colonization and infection are two very different concepts," McCormick said, "and treating colonization as infection in classifications can cloud our ability to track infectious outbreaks effectively."

To the question of whether undetected asymptomatic colonization of C difficile misses opportunity to remediate and reduce transmission among hospitalized patients, McCormick acknowledged that, "decolonization in general is certainly a contentious issue in infection control right now."

He suggested, however, that the evidence for monitoring, detecting and treating colonization is stronger for Staph aureus than for C diff. "Costridioides species are widespread in the environment and at least about 5 percent of the general population is colonized with C diff, since these types of organisms can be found everywhere."

"Colonization can also be temporary," McCormick pointed out, noting the adverse effect to the microbiome of antibiotic treatment. "Thus, I think it can be worrisome to treat people who are colonized with C diff empirically simply because they are colonized at that time."

McCormick does advise diligent hand washing, however, and thorough cleaning of hospital rooms between patients, with particular attention to high-touch surfaces. "This, along with good antibiotic stewardship, goes much further than testing everyone for C diff and treating if deemed colonized, in my opinion, toward reducing C diff infections," he said.

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