Here we go again: Active detection and isolation, C. difficile edition

An interesting study in JAMA Internal Medicine, likely to generate a lot of discussion, addresses the use of “active detection and isolation” (ADI) for control of C. difficile disease. This quasi-experimental, single-center study employed PCR screening (tcdB detection) of all patients admitted through the emergency department (patients admitted from other locations were excluded, as were “short stay” patients), and those that were found to carry toxigenic C. difficile were admitted into a kind of “quasi-isolation”—gloves were used, but not gowns or private rooms. So all-in-all, a very pragmatic (and somewhat idiosyncratic) intervention. Healthcare-associated C. difficile disease rates declined after the intervention, which students of prior quasi-experimental studies of ADI for MRSA and VRE will find unsurprising. 

At this point, I will outsource my blog post to Jon Otter and Martin Kiernan at the Reflections IPC blog. Go on, head over there for an excellent pro-con post about this study, and vote on the question posed at the end of the post. Then come back here to read my only additional observation…..I can wait (spoiler alert: I agreed with Jon).

OK, you’re back: the only thing I have to add to Jon and Martin’s excellent post is this: we’ve been here before. Recall the persuasive quasi-experimental studies (many single-center, some multicenter) of MRSA and/or VRE ADI published over the course of a couple decades. When better designed studies were eventually performed and published (e.g. STAR*ICU, REDUCE-MRSA, MOSAR, this one by Harbarth and colleagues that doesn't have a catchy acronym)—you know, studies that included concurrent control groups (control groups are for losers!), it became evident that ADI wasn’t the key to MRSA or VRE control. I think we’re headed down that road again, this time with C. difficile. Who’s going to step up and organize the multicenter, cluster-randomized trial we need to do now? Or perhaps better to ask: who is going to pay for it?


  1. Well said Dan, couldn't agree more! Jon Otter also made some excellent points in relation to this study in his posting.

  2. Screening provides affirmation to the ordering provider that subsequent testing, during the admission, is not warranted.

    If I screen a patient and she/he is positive (colonized) and later develops hospital onset diarrhea, I have no need to test (I know the answer) and can treat empirically. If I have screened all of my admissions and know their colonization status, there is little reason to retest during or following their hospitalization and “hospital onset” cases (aka. colonization in the setting of non-infectious diarrhea) plummet. The argument against this is that the oral agents used to treat CDI decreased, rather than increased during the intervention phase. In this case, screening may have made the difference but not necessarily via stopping transmission as the pro-ADI proletariat would have you believe but by altering the clinical decision making of the ordering providers who subsequently avoided indiscriminate testing.


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