Thursday, December 20, 2012

Should we go over (to) the Cliff?

There's been a lot of talk in the US about "the cliff," specifically the fiscal cliff. Should we go over the cliff? Is the cliff just a curb?  What should we do? Panic! In response, the GOP has started pushing "Plan B," which will apparently require all Americans to receive emergency contraception if they're pregnant. This has some merit since if we no longer exist, we can't really run up the budget deficit, now can we.

Anyway, this is ostensibly an infection prevention blog, so I better get back on topic.  In the annual Christmas issue of the BMJ, investigators from the Netherlands have reported a novel method for speeding up the diagnosis of Clostridium difficile infection. The name of their novel method?  Cliff.  Just as I expected, they call or email the CDC and ask Cliff McDonald what he thinks! NO? What?

It turns out that they've trained a beagle named Cliff to diagnosis C. difficile by smell (thank goodness it's not taste). Anyone who has done an ID fellowship or even a medical internship gets pretty good at recognizing the unique small of C. diff, so we know this could work. It turns out to work pretty well. Cliff's nose detected C. difficile positive clinical samples with a sensitivity of 83% and a specificity of 98%. Not too shaggy.

Addendum: A 2007 CID study reported self-selected nurses had a sensitivity of 55% and specificity of 83% in diagnosing C. diff, while an earlier study reported that nurses had a sensitivity and specificity of 84% and 77% for predicting C. diff using factors that included odor. I would like to see Cliff dual it out with these nurses in a future trial. Daniel Uslan suggested Cliff vs "Sniff": an RCT.


  1. Nice post, Eli!

    I know that many techs in micro labs claim to be able to smell C. diff, but I recall a study from a few years ago (in ICHE, I think) that found when formally tested, techs were not able to identify C. diff by smell. However, I suspect that Cliff's nose is far superior.

    I also recall a talk by Scott Wiese regarding dogs in hospitals having the potential to spread C. diff, which makes me a little worried that Cliff is a self-fulfilling prophet.

  2. Thanks Mike. I posted an addendum with the two studies (mentioned in the BMJ paper too) that measured the sensitivity and specificity of clinical nurse prediction of C. diff; one of the studies allowed inclusion of other factors in their prediction and the other only included nurses who claimed to be good at detecting C. diff via odor; so both have limitations. I think this is worth a comparison trial. Also, I agree that we need to be worried about diagnostic and companion animals as vectors - I'm starting a company now that will sell isolation gowns and gloves for beagles....

  3. I'm not surprised by the amount of coverage in the last press this is getting, it's a cute story, and I love dogs. But it misses 1 in 5 cases? Now if the dog could also ask about antibiotic exposure and abdominal symptoms...
    I remember seeing a study a while ago that looked at aromatics (in the technical sense) assoc with C.diff (hard to find on my phone - perhaps Garner CE, FASEB J 2007?) that may be what Cliff is sensing.
    When it comes to animal diagnosticians, Oscar (Dosa, NEJM 2007) still wins in my book, even though he's a cat.