Jarrod Shapiro, DPM Practice Perfect Editor Assistant Professor Dept. of Podiatric Medicine Surgery & Biomechanics College of Podiatric Medicine Western University of Health Sciences St. Pomona, CA

Why? How? Part 1

Why?

I ask these questions a lot. When in clinic with my students and residents, I constantly ask these two question. I think it drives my trainees crazy, though they'll never tell me out loud.

I ask why and how questions like, "How do you know this patient needs this surgery?" or "Why does your patient need preoperative antibiotics?" or "How do we know orthotics reduce foot pain?" The purpose, of course, is to start my trainees thinking. I don't want them to simply believe everything I tell them just because I'm their teacher. I don't know everything, but it's so easy to give sudents the impression that everything is known, and medical knowledge is black and white. Of course, in reality medical knowledge is grey.

Here's a quick example. Many of us palpate extremity pulses as part of our physical examination to diagnose peripheral arterial disease (PAD). So, I'll ask YOU: How accurate is this examination technique for diagnosing PAD? You might say, "In my experience, I have been very successful diagnosing PAD with pedal pulse palpation." But in our modern world of evidence-based medicine, "my experience" is not enough to answer the question. The follow-up question to my first one is how do you know you're successful? This is the point where my students start becoming impatient with me, because invariably the answer is, "I don't know." The actual answer IS known, so we'll get to that a bit later.

So much of what we know about the world around us, whether in podiatric medicine or life in general, comes from someone telling us. Most of the time, we don't question what's "true", taking our information source at its word. But all too often, what we've taken for granted as true turns out to be false. Take for example the idiom, low man on the totem pole. Most of us believe it arises from the Native American totem pole and means the least important person in a certain hierarchy. In reality, the phrase originated from the opposite meaning. The carving closest to the ground actually was the most important and was done by the master carver while the highest was completed by the least experienced person, since this is furthest away from the viewer and mistakes were harder to see.

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Unfortunately, we spend a small amount of time questioning the world around us and even less time in college learning to do so. This, of course, is the basis of critical thinking. I urge all of our readers to question your perceived reality as often as possible and to not take for granted what the supposed authorities tell you. This is the strength of evidence-based medicine which provides a framework in which we find the best evidence to answer our why and how questions.

For those of you interested, here is a very quick primer on how to create and use a clinical question to find the answer to your burning questions. First, remember PICO. This is a mnemonic to recall how to create a clinical question.

P = Patient
I = Intervention
C = Comparison
O = Outcome

As an example, I might ask the following question: In asymptomatic patients [Patient], is palpation of pedal pulses [Intervention], as successful as angiography [Comparison], in diagnosing peripheral arterial disease? [Outcome]

The next step would be to insert the key words of this question into the search area of your favorite medical search engine (PubMed, in this case) and then evaluate the resulting literature for quality. This part takes the most practice, so take some time and experiment with it.

Unfortunately, based on a rapid search of PubMed, there is no such study that compared these two diagnostic methods. However, a broader search of physical examination techniques did find an interesting study published in JAMA in 2006.

You'll be happy to know that in patients without other symptoms, the absence of one pedal pulse is helpful to diagnose PAD (with a likelihood ratio of 3.10 at 95% confidence interval).¹

Finding a good answer to the "why" and "how" question is not difficult with a little practice. The first step, though, is to stop taking what we know for granted and start asking the why question in the first place.

In next week's issue, I'd like to look more broadly at critical thinking and how we can protect ourselves from those trying to manipulate our thoughts and feelings. Until then, keep questioning!

Best wishes,

Jarrod Shapiro, DPM
PRESENT Practice Perfect Editor
[email protected]

Reference

1. Khan N, et al. Journal of the American Medical Association. 2006;295(5):536-546.

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