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

How important is it to make the correct diagnosis?

Sounds like a stupid question, right? Doesn’t medicine revolve around making a diagnosis (or at least a differential diagnosis)? Is that not the first and necessary step to instituting appropriate care for a patient? What if there’s more than one diagnosis? Can one diagnosis be a confounding variable for another?

With your indulgence, I’d like to illustrate my point. About a month ago my car started making a peculiar sound. Whenever I reached a speed of 45 miles per hour, I would hear a slight tapping sound coming from the front driver’s-side wheel area. At speeds below this, no sounds. Beyond 45 miles per hour, the sound would worsen slightly.

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As a side note, I’m not too fond of driving slowly. I think someone secretly added lead into my right foot (Is there a CPT code for that?). For a while, I thought it a strange coincidence that none of my cars would do 30 miles per hour. The car would automatically accelerate from a stopped position to at least 50 miles per hour regardless of the posted speed limit! Does anyone else have this problem with their cars? Maybe it’s just me….

Anyway, I tried to figure out the problem myself (a ridiculous thought since I know nothing about cars). I looked under the car, in the wheel well, under the hood. I tried to correlate the “history” with my “physical exam” in good-doctor manner. Unfortunately, I couldn’t figure the thing out (Too bad the car couldn’t give me its history!).

I decided to bring it in to the repair shop. Now I should tell you I knew the brakes probably had to be changed, since they were starting to grind (no doubt as a result of my excessive speeding and rapid stops!). However, the sound seemed to come from the rear of the car — not the left front tire area.

Later that same day, the repairman called to tell me what the problem was. “It’s your rear brakes,” he said. “They need to be replaced.”

“My rear brakes are making that tapping sound only when accelerating past 45 miles/hour?” I asked incredulously. “Why doesn’t it happen when I’m braking?”

“Well,” he said after a couple of seconds’ pause, “Your brakes are down to the metal. When that happens, the brakes sit slightly differently in their housing, allowing them to move. They must have been rubbing against something.”

It sounded like a reasonable explanation, I thought (not knowing anything about brakes), so I gave him the approval to do the work (along with a couple of other things that needed to be repaired – amazing how that happens isn’t it?).

I picked the car up that evening and drove home $800 poorer. In spite of the cost, I was happy to hear no further tapping… Until I hit 45 miles per hour.

As my face reddened and my blood pressure started rising, I realized the true cause of the tapping sound: a rubber seal on the left headlight had started pulling out of its slot and was slapping against the car! The sound occurred only above 45 miles and hour because the wind resistance was not strong enough at lower speeds to pull the seal out of its housing.

A little crazy glue has completely resolved the problem.

So here’s my point. When diagnosing my car’s problem, the repairman found the most obvious diagnosis — in this case the wrong one — and created an explanation that fit his diagnosis. He should have correlated all the information to find the best diagnosis that explained the complaint. It’s not appropriate to pick an explanation that fits into your presumed diagnosis.

The same is true with medicine. We must be cautious not to pre-pick a diagnosis and squeeze the explanation into that diagnosis. Our diagnosis must explain the patient’s symptoms. For example, hallux valgus is an obvious diagnosis, but it may or may not explain a patient’s forefoot pain.

We need to be better than my mechanic. Consider your diagnoses carefully, but reconsider if the story doesn’t fit. Best wishes, fellow diagnosticians.