There’s an old saying in medicine, “When you hear hoof beats, think horses, not zebras.” In other words, most headaches are not brain tumors, low back pain not herniated discs, and unusual rashes not measles. On this last one, unfortunately, we can no longer be certain.
Still, it is the physician’s duty to ensure that any medical complaint does not indicate the rare and ominous. Often, a thorough history and physical are all that is necessary. Going off on a wild goose chase (OK, that’s two animal metaphors already) wastes time and money, causes anxiety for the patient and can result in misleading information that, in turn, perpetuates the chase. Remember, there are an estimated 60 million horses worldwide and about 700,000 zebras.
A zebra turns up in horse’s clothing
Other than her natural dark curls and deep blue eyes, this patient had nothing remarkable about her. And I mean that in the best way possible. In her first year she grew normally, achieved her developmental milestones a bit ahead of schedule and was an adventurous eater. She had a few colds and an occasional ear infection, but nothing that seemed excessive. No alarm bells were going off in my head, which allowed me to concentrate with her first-time mom on the usual challenges of Year One.
So I was taken aback when her mother asked at her one year well exam if we could “check to see if her immune system is OK, ‘cause she’s had a lot of infections.’”
The last patient I had with an immunodeficiency had significant infections, including one in the lungs and another in a joint, that occurred over a very short span requiring extended hospital stays.
Nothing said immunodeficiency in this child – her illnesses were common and mild. They were average in number. They resolved as I expected them to without complications, and she was thriving.
Dancing around the pros and cons
But when a parent or a patient requests a lab or other tests to address a concern, you become involved in a very delicate dance.
First, make sure you fully understand their concern and what they think might be the cause of the problem. Second, determine whether the tests they want are related to the complaint. If they are not, let the patient know what tests may be appropriate instead.
Third, weigh the costs of the test versus the probability it will reveal a new diagnosis (if someone has a mathematical formula for this that is understandable, please forward it). Fourth, balance the level of concern: Will your word be enough or will a normal test be more reassuring? In pediatrics, the additional parental angst of caring for a child should never be underestimated. And finally, always have a plan when you get a result you were not expecting.
Factoring all of the above (remember, you have to do this quickly and in real time), I decided a few simple tests were reasonable. I checked a white blood cell count and immunoglobulins – proteins that function as antibodies in the bloodstream. That should be sufficient I felt. And I admit I thought little more about it after they left the office.
Results surprised me more than anyone
Of course you know what comes next: While her white cell count was normal, I was shocked to find she had almost no measurable immunoglobulins. What this meant was, that without treatment, she was at significant risk for severe bacterial infections as she lacked the usual defense mechanisms to combat these types of diseases.
Could the results have been a mistake? No. The lab had already rechecked to verify.
I immediately read up on the disorder, trying to figure out what I had missed. I couldn’t find anything. I sent her to our pediatric immunologist, whose first question to me after seeing her was: “How did you figure this out? I never would have thought of looking. Her history didn’t indicate it.”
I could have bamboozled him with some nonsense about a sixth sense, but instead I told him I ordered the labs to appease mom. It is nice when a subspecialist is impressed by your prep work, but that does not give you license to claim credit for stumbling upon an acorn in the dark.
Learning from the zebra lesson
So while she receives immunoglobulin on a regular basis – which will allow her to live a full and productive life – I am left to grapple with a few dilemmas. How many more patients like her are out there that I have missed? What do I do the next time a parent asks for these types of tests (hopefully, go through the same thought process)? What about those children with a similar pattern of illness that the parents are not concerned about – do I screen these children? To what extent do I allow one case in 30 years of practice to alter my decision-making? What is the cost of doing a large volume of tests to find that one needle in a haystack?
All of us who have practiced medicine long enough have found zebras lurking among the horse herd. Though it is not a reason to radically alter your method of practice – sins of commission are as equal to those of omission – they are a good reminder for vigilance.
Postscript: She came in for her four year well-check recently with mom and younger brother (who thankfully does not have the disease). She is growing well, good language skills, smart as a whip, very engaging. On her way out she stuck her head in my office and said, “OK, Dr. Ezzo, I’ll see you later!” Just a couple of friends who had been chewing the fat. Is this a great job or what?