Appropriate C Difficile Testing May Vary by Hospital Setting, Physician

Investigators observed that nearly half of all Clostridioides difficile tests conducted at a Korean teaching hospital were done so inappropriately, according to a new study that highlights continued need for improved and communicated diagnostic stewardship for the gastric infection.

In new retrospective analysis data from Seoul National University College of Medicine, investigators reported significant differences in rates of inappropriate C. difficile testing based on the clinical setting and prescribing clinician’s profession. The team additionally observed via questionnaire that physicians’ confidence in ordering an appropriate C difficile test may also vary.

Led by Dr. Hee Bum Jo, of the division of infectious diseases in the department of internal medicine at Seoul National University Bundang Hospital, the research team conducted a retrospective review of patient medical records at a 1300-bed tertiary-care teaching hospital who were tested for C difficile infection from September - November 2019. They additionally conducted a physician survey to assess the knowledge and ordering patterns of testing for such infections.

As the most common healthcare-associated infection, C Difficile prevalence in Korea alone had increased more than 3-fold from 2008 to 2011—while nations including the US have reported increasing greater management of the infection. Investigators cited the 2017 Infectious Diseases Society of America (IDSA) and the Society for Healthcare Epidemiology of America (SHEA) guideline updates recommending testing in relevant clinical settings, defined as instances of unexplained and new-onset ≥3 unformed stools within 24 hours, to improve the reliability of the various available C difficile laboratory tests.

“Although asymptomatic colonization is not an indication for treatment, the C difficile nucleic acid amplification test (NAAT) and glutamate dehydrogenase (GDH), the currently used methods cannot discriminate between CDI and asymptomatic colonization with C difficile, which results in overdiagnosis and overtreatment,” they wrote. Therefore, there is a need to consider the relevant clinical situations and symptoms for effective CDI diagnosis.”

Jo and colleagues’ analysis included 715 tests from 520 patients. They classified testing as either hospital-onset or community-onset, and they used an algorithmic method to define appropriate or inappropriate testing. Patients were ≥18 years old, did not receive outpatient testing, and did not have colostomies.

A total of 576 tests were hospital-onset, having occurred >3 days after admission or transfer from another hospital; the remaining 139 were community-onset. Of the hospital-onset tests, nearly two-thirds (n = 355 [61.6%]) were conducted having met IDSA and SHEA’s ≥3 unformed stools in 24-hour criteria, and the remaining 221 (38.4%) did not.

Of the tests of patients with ≥3 unformed stools, 282 (49.0%) did not include laxative use in patients; 73 (12.7%) included laxative use <48 hours prior to the test. Just 15 tests (2.6%) were conducted when patient had shock or were positive for ileus.

The team concluded that 297 tests (51.6%) for C difficile were conducted appropriately based on the recommended in-hospital guidelines, while 279 (48.4%) were conducted inappropriately.

The appropriately tested group was equally conducted in the hospital’s general ward (81.8%) as the inappropriately tested group (86.7%; P = .1.06). But the former group were far less conducted in the emergency room (0.3%) than the latter group (5.0%; P <.001).

The appropriately tested group additionally had greater proportions of internal medicine physicians ordering the test than the inappropriately testing group (72.4% vs 63.4%; P = .021). Investigators observed no differences in the 2 groups’ median number of days between admission and testing.

The team observed a significantly increased risk of inappropriate testing conducted in the emergency room (odds ratio [OR], 20.06; 95% CI, 2.60 - 154.78; P< .004), and a decreased risk in the intensive care unit (OR, 0.33; 95% CI, 0.18 - 0.61; P = .001).

In their survey of 61 physicians, investigators observed significantly higher mean scores on the 10-point score among internal medicine physicians (7.1) versus other physicians (5.7; P = .001).

“Specifically, the question regarding repeat testing had the lowest correct answer rate (36.7% in internal medicine physicians; 38.7% in non-internal medicine physicians; 37.7% in total population),” investigators noted. “There was a significant between-speciality difference in questions regarding culture testing, toxin EIA with GDH EIA testing, GDH EIA with culture testing, and requirement of test of cure.”

The team concluded that this assessment—potentially the first to assess the appropriateness and physician practice patterns in a country with a growing burden of C difficile—showed institution-specific lanes of improvement for diagnostic stewardship.

“Diagnostic stewardship for CDI should be implemented, particularly through educational interventions for those working in the emergency room and for non-internal medicine physicians,” they wrote. “Prospective multicentre studies on the effectiveness of diagnostic stewardship are warranted.”

The study, “Prevalence of and factors associated with inappropriate Clostridioides difficile testing in a teaching hospital in Korea,” was published online in Antimicrocial Resistance & Infection Control.