There has been debate among hospital epidemiologists whether to ban white coats, ties and long sleeve shirts in order to reduce transmission of MDR-bacteria in healthcare settings. One of the arguments used against banning certain elements of physician attire is that there isn't enough data to prove that transmission occurs from said attire to patient. Of course there aren't any randomized trials showing that banning white coats reduces MRSA transmission, but is this a fair argument? I don't think it is and my reasoning has to do with a concept called action threshold that physicians use when making decisions, but rarely discuss.
The action threshold is the probability of an outcome at which it makes sense to undertake a specific intervention. In this case, how sure do you need to be that white coats or ties are harmful to patients before it's worth banning them? A useful clinical example is the use of the Centor Criteria to diagnosis strep throat (or better to rule it out) based on history and physical and treat with antibiotics without getting a throat culture. Do you really need to be 100% sure they have strep throat before giving antibiotics or is 60% good enough? Of course, before you diagnose someone with HIV or cancer you need to be close to 100% sure you have the right diagnosis because the treatments are so harmful.
In Richard Gross’s book he derived a formula: Action Threshold = Harm/Improvement, where harm is the adverse events associated with the intervention and improvement is how much better the patients are with the intervention compared to without the intervention. If expected improvements outweigh potential harms then the intervention should be considered; the action threshold is the tipping point in modern parlance. All of this flows from the the expected utility model developed by John von Neumann and Oskar Morgenstern, but I digress.
So, how certain do we need to be that removing white coats (or ties or long sleaves) will benefit patients before pulling the trigger on an all out ban? What harm could possibly occur from such a ban? How would this hurt patients - I would say not at all and physicians could certainly find another way to uphold their professional standing. The white coat ceremony didn't even exist prior to 1993 at Columbia University, so how sacred could these stained, unwashed garments really be?
Semmelweis suggested that hand washing could prevent infections and save lives years before Louis Pasteur confirmed the germ theory. How many lives could have been saved if physicians listened to him in the interim? In fact, not enough people even listen now! How bad will we feel if future investigators prove by cluster-randomized trial that white coats harm patients? White coats need to go and when white-coat backers complete the trial showing they are safe and can actually stay clean between patient visits, we can let them back in our hospitals. Until then the burden of proof should be on those that want to keep white coats; use the action threshold and do the right thing.