The Hoofbeats of Zebras

Although I have been exclusively engaged in healthcare coaching for nearly two years, one of my favorite parts of my teaching career was hearing an elegantly articulated patient case presentation, building a differential diagnosis, and then going to the bedside with my team. More often than not, I would confirm my team's findings; however, there were times when I discovered aspects of the patient's exam—whether physical or historical—that had been overlooked.

Today, as I was speaking to a client about his personal statement, we veered into a conversation about the importance of considering a broad differential diagnosis when listening to a patient or hearing a case presentation. We agreed that while an experienced clinician can often arrive at a correct diagnosis relatively easily, as physicians, we must all guard against the potential danger of "premature closure." This occurs when we fail to consider alternatives after forming an initial diagnosis. Such mistakes are not uncommon and often arise due to anchoring bias, where we are tempted to focus on certain notable features of a patient's initial presentation and cling to our first impressions—even when new information comes to light.  

We discussed how, as internists, it is our natural inclination to enjoy diagnosing those less common diseases that are statistically unlikely but may, on occasion, turn out to be the correct diagnosis. As a general rule, we learn to keep such diagnostic considerations in reserve, but revisit them if our patient is not improving or if new contradictory information is discovered that brings our initial diagnosis into question. 

This led me to share a tale from my days as a medical student, when, in an attempt to be comprehensive in my first H&P write-up, I included some rather far-fetched differential diagnoses.   In fact, the rather senior internal medical physician who was my attending handed back my paper with the following comment:  "Wow!!! Let's talk."  I must have been somewhat embarrassed at the time, but now I look back and smile.  I can't quite remember the details, but for my patient, a 60-year-old male with a strong tobacco history, weight loss, cough, and a necrotizing chest mass, I had bizarrely included in my discussion the possibility of paragonimiasis - a most improbable diagnosis.  Unfortunately for him, yet quite predictably, his diagnosis ended up being lung cancer. 

And fortunately for me, my attending used this as a teachable moment." It was then that I first learned the phrase, "When you hear the hoofbeats of horses, don't expect to see a zebra,"—a phrase I now know was coined by Dr. Theodore E. Woodward. Over the years as a clinician, I've encountered a few zebras and remember each one's unique stripes. In fact, I liked zebras so much that as a medical student, I owned a set of "Zebra Cards: An Aid to Obscure Diagnosis," a classic teaching tool in the form of a deck of cards focused on rare diseases.

So, now, in my role as a residency application coach, why am I writing about zebras, apart from having enjoyed this discussion with my client? Quite simply, because I believe this topic is relevant to residency applications. Searching for your own zebras—those unique aspects of your personality or experiences that aren't typically included in an ERAS application—and writing about them may surprise program directors, who often hear the expected hoofbeats of horses from most applicants. And such a surprise can truly delight.