Discussion

Inappropriate C. difficile testing is common at acute-care hospitals and has numerous consequences. ^{Reference McDonald, Gerding and Johnson1,Reference Rock, Pana and Leekha2} Reducing unnecessary testing at the ordering stage is ideal because it averts wasted downstream efforts involving specimen collection and test processing. In our survey, 62% of respondents reported providing clinical decision support when orders were placed but only 28% reported use of a “hard stop.” Although various investigators have reported that implementation of a “soft stop” or a “hard stop” can reduce inappropriate C. difficile testing, Mizusawa et al ^{Reference Mizusawa, Small and Hsu3} sequentially used both and reported that “hard stops” may be more effective than “soft stops” at mitigating inappropriate orders. ^{Reference Mizusawa, Small and Hsu3–Reference Madden, German Mesner, Cox, Mathers, Lyman, Sifri and Reduced6}

The laboratory can also help to mitigate unnecessary C. difficile testing. As recommended in published guidance, 90% of respondents reported that their laboratory cancels C. difficile orders on formed stool. ^{Reference Pillai7} A smaller group (9 of 50, 18%) reported that their laboratory rejects samples based on recent history of C. difficile testing.

Once a C. difficile test has been processed, there may still be opportunities to prevent unnecessary treatment. Half of our respondents described using a multistep algorithm that includes toxin EIA and affirmed that laboratory-issued C. difficile test reports advise providers to consider the possibility of colonization in toxin-negative patients. The clinical relevance of NAT-positive, toxin-negative C. difficile cases continues to be studied. ^{Reference Polage, Gyorke and Kennedy8} In a case-control study involving 4,878 patients diagnosed with CDI using a GDH-based algorithm, Guh et al ^{Reference Guh, Hatfield and Winston9} reported that toxin-positive cases were more severe and experienced CDI-related complications more frequently than patients who tested positive by NAT only. However, 49 of the toxin-negative cases developed toxic megacolon, and 8 required a colectomy. Although patients who test toxin negative may be less likely to develop severe disease or complications, the absence of toxin does not exclude the possibility of either. ^{Reference Polage, Gyorke and Kennedy8,Reference Guh, Hatfield and Winston9} This nuance should be clear in laboratory report verbiage, and test results should always be interpreted in conjunction with clinical findings.

In the current survey, only one-third of respondents reported that their ASP performs audit and feedback based on positive C. difficile tests. The role of ASP in C. difficile management has been evolving and reports of active ASP interventions to date have been sparse. In a single-center quasi-experimental study of 208 patients being treated for CDI, Hecker et al ^{Reference Hecker, Son, Alhmidi, Wilson, Wiest and Donskey10} reported a modest reduction in mean days of unnecessary CDI treatment after implementing audit and feedback on positive C. difficile test results (1.4 days vs 0.4 days; P = .02).

This study has several limitations. With only 50 respondents, the sample size was small. Also, 76% of respondents identified themselves as an academic medical center or an institution with an academic affiliation, which may limit generalizability of our findings to nonacademic hospitals.

In summary, this survey showed that while C. difficile diagnostic stewardship interventions were common, strategies that actively block inappropriate C. difficile orders were uncommon as was active intervention of ASPs on C. difficile test results. Institutions that have not successfully reduced reported C. difficile rates using educational interventions and “soft stop” BPAs may wish to consider methods that actively block inappropriate test orders.