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Contaminated Stethoscopes COULD Be Harmless

mrsa_magn_lgAn interesting study is making the rounds in the mainstream media.

Instapundit, Scientific American, NBC News, Healthcare Business Tech Blog, MedPage Today, CBS Atlanta, and Consumer Reports have all reported on the study.

Unfortunately, the study draws questionable conclusions.

A group of scientists at the University of Geneva Hospitals (Switzerland) and affiliated with the World Health Organization recently published a study demonstrating that physicians’ stethoscopes harbor many bacteria. The study was titled “Contamination of Stethoscopes and Physicians’ Hands After a Physical Examination” and was published in this months’ Mayo Clinic Proceedings.

First, the researchers note that physician stethoscopes can be contaminated after a physical examination. Agreed.

The amount of contamination can be as much as that contained on the palm of the hand (but not the fingertips). OK wonderful.

The number of colonies causing the level of contamination is “substantial” after a single physical exam. For fingertips, the average number of colony forming units transferred was 467. For stethoscopes, the average number of colony forming units transferred was 89. Not so sure that is “substantial,” but we’ll go with it. For MRSA carriers, the average number of CFUs transferred was 12 for the fingertips and 7 for the stethoscope. However … no transfer of any MRSA bacteria occurred in 24% of patients and the researchers just discarded the data from those patients for the final analysis. (“Because MRSA was not recovered from the physicians’ dominant hand or the stethoscope after the examination of 12 of 50 patients colonized with MRSA (24%), these patients were excluded from the final analysis”). Averaging in a bunch of data that don’t fit with their conclusions would only dilute their message.

Then come the “scientific” conclusions:
“By considering that stethoscopes are used repeatedly over the course of a day, come directly into contact with patients’ skin, and may harbor several thousands of bacteria (including MRSA) collected during a previous physical examination, we consider them as potentially significant vectors of transmission. Thus, failing to disinfect stethoscopes could constitute a serious patient safety issue akin to omitting hand hygiene.”
Note the hypothetical pseudoscience contained in just these two sentences.

  • Stethoscopes “MAY harbor several thousands of bacteria” – meaning that stethoscopes also “may NOT harbor” several thousands of bacteria and you haven’t proven anything.
  • “WE consider them as potentially significant” – ah, the logical fallacy of an appeal to authority. WE are published in a national journal and are getting national media attention. No one else might consider them as potentially significant, but those who do not agree with US are obviously unqualified to make such decisions. Oh, and by the way, WE still haven’t shown any literature proving this point, so just believe our pseudoscience and move along.
  • “THUS …” – a haughty prelude showing that you are trying to use your unfounded conclusions to get everyone to believe your ultimate point that …
    “failing to disinfect stethoscopes COULD constitute a serious patient safety issue” – BRILLIANT! Oh, and by the way, the moon COULD be made out of green cheese, the government COULD be putting nanobots in our vaccines, Juan Pablo COULD marry any woman he wanted on the Bachelor, and I COULD win the lottery. Without better research, there is no way to determine whether any of these possibilities is more likely to occur than any other of the possibilities.
    A scientific statement that something “COULD” occur is close to being meaningless, showing only the absence of an impossibility. The likelihood of that event occurring is anywhere between 0.0000000000000000001% and 100%.

There are multiple parallel studies which also make leaps in logic about the possibility of disease transmission from other fomites.

Think about all the tourniquets that hospitals and labs purchase every year then discard after a single use … to avoid the spread of infection. Are there any studies showing that changing non-contaminated tourniquets on every patient has decreased the transmission of disease? I couldn’t find any.
I did find one study from 2001 noting that “tourniquets MAY act as reservoirs of pathogenic organisms and COULD therefore pose a risk to patients through cross-infection,” but also noting that despite the “poor infection control practices” there was a “relatively low frequency of S. aureus contamination of tourniquets.” Nothing about transmitting infections.
I also found a study noting that contamination of tourniquets appeared to be from a phlebotomist’s hands, not from a patient’s skin.
Finally, I found a 2012 study showing that 18 out of 50 tourniquets collected from a variety of sources in a UK hospital were “positive for S. aureus,” that 6 out of 50 “were MRSA positive,” and that only 20 of 50 tourniquets “appeared clean.” Based on these findings, the authors concluded that “Non-disposable venepuncture tourniquets are contaminated with MRSA and pose a risk to patients.” Note the leap in logic from 12% positive for MRSA in the study to the insinuation that all tourniquets have MRSA in the conclusion. Based on their overwhelming study of 50 tourniquets showing potentially six contaminated specimens, the authors felt comfortable concluding that all over the world “the use of non-disposable venepuncture tourniquets should be abandoned.”
Despite all of this tourniquet “research,” the World Health Organization’s guidelines for best practices in phlebotomy do not include a recommendation to discard a tourniquet after each blood draw.
So, based on what appears to be largely junk science, hospitals and labs now routinely discard tourniquets after each blood draw. With 35 million admissions, 51 million inpatient procedures and 100 million outpatient procedures each year, the number of tourniquets that must be purchased by hospitals (who pass the costs on to patients) and then trucked to landfills is probably on the order of about 200 million each year. What a waste of money and resources.

Don’t forget about the “white coats will infect us” study as well. Same lame conclusions, same lack of evidence. Also see Skeptical Scalpel’s take on the same study.

Researchers fail to realize that humans NEVER interact in a sterile environment – if you venture outside of a sterile bubble, you’re going to be exposed to germs. Everywhere. Scientists even found “extreme” bacteria in NASA “clean rooms” which are designed to be completely sterile. Hospital doorknobs, elevator buttons, chairs, magazines, toilet seats, cafeteria trays, money, faucets, soap dispensers, blood pressure cuffs, exam tables, the paper covering the exam tables … all have bacteria.
Wait a minute. Does the white paper on an exam table even prevent the spread of bacteria? Oh nevermind.
Are we going to ban all these other potential sources of MRSA colonies as well? Or maybe we should just publish a paper recommending that we scrub every such item really really well every time it touches something else that could also be contaminated. Can’t be too careful, you know.
I’m not saying that we should lick our fingers after juggling bat guano, but at some point there has to be a limit on needless rules based on junk science.

Show me research showing a significant decrease in MRSA rates after implementation of disposable stethoscopes/tourniquets/white coats/hospital beds/hospitals, then we can make a cost analysis to determine whether making such changes are cost-effective. Until then, leave the unsubstantiated assertions back in the faculty lounge.

In the stethoscope study, the Geneva researchers asserted

Our findings provide strong evidence of the potential for stethoscope-mediated transmission of microorganisms and the need to systematically disinfect stethoscopes after each use.

No. They don’t. Now go back and do some additional research about the clinical effects of the recommendations you make, then get back to us.

I suppose that the Mayo Clinic Proceedings COULD publish the peer review comments on this study prior to its publication so that everyone could determine whether or not the peers even considered the scientific validity of the conclusions being made.

I’m betting the likelihood of that occurring is about as likely as getting a confirmed MRSA transmission from a stethoscope.


  1. Was this study funded by the makers of those shitty disposable stethoscopes with the yellow tubing that are used in hospital isolation units?

  2. And once again, Aliens Cause Global Warming.

    “Michael Crichton: Aliens Cause Global Warming, Michelin Lecture to Caltech, 2003”

    Don’t be too harsh on the idiots who got permission to publish this garbage.
    Making ignorant bumpkins too scared to visit the hospital under the Unaffordable Care Act may be a feature, and not a bug.

    And the Mayo Clinic isn’t all bad; I love their sandwich dressing on a nice BLT. But clearly the World Health Organization is well on the way to becoming an oxymoron on par with “jumbo shrimp”.

  3. Does this mean we have to clean everything down with 2% chlorhexidine, a la Chuck Denham?

  4. I am more worried about medical personnel’s lab coats.

    I have worked in labs for over twenty years. Our lab coats are used to protect us and never leave the lab. We use disposable lab coats for animal work or highly infectious work.

    At our university, med and nursing students, doctors, nurses and other medical personnel wear their lab coats everywhere. It seems like the lab coats are a badge of honor. As a patient, I often wonder where the lab coat has been and what it was exposed to.

  5. I just assumed doctors wiped them down just as they wash their hands in between patients when in the hospital.

    ” Does the white paper on an exam table even prevent the spread of bacteria?

    Actually …I have often wondered how that strip of white exam table paper that doesn’t even cover the entire width protects nekkid women sitting on it for gyne/uro appts.? Does it really protect the spread of some STD, etc.? I really would like to know.

    *Can anyone answer this?* I’ve never caught anything like that …but …

    *How does paper prevent something from transferring to another patient?*

    Especially some gross ..contagious condition. They wipe it down in between patients ..but does it kill everything? UGH!

    Anyway …NOW …this GERMAPHOBE is taking a shower. I really am … because I’m going shopping in a bit. But …I am sure gonna love this shower and feel grateful that no respectable germ will be left when I’m done. ;)

    I’m increasingly convinced in this life …with so many things going on, threats, etc., that all we can do is our best (and do strive for best) and then let God do the rest. :)

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