State & Local Government Policy, Business and Technology

When You Hear Hooves, Think Horse, Not Zebra

Data-Smart City Solutions: A month or two ago I was having a discussion with a physician about obscure diseases — commonly referred to as zebras. While I was considering these zebras in the context of effective data mining strategies for medical diagnosis, he made an interesting point. One of the things that they teach new physicians is the phrase “When you hear hoofs, think horse, not zebra.” The principle is quite simple — the odds are the patient has the more common diagnosis than a rare, improbable one. A simple but illustrative example would be the following (stolen from a physician family member):

An adolescent female patient presents with a three-week history of headache, fatigue, and intermittent fevers but was historically healthy. The physical exam was unremarkable and aside from the occasional fevers, the only symptom of note was that she was pale in color. The zebra could have been meningitis or a brain tumor — and the inexperienced practitioner would order thousands of dollars of tests and subject the patient to multiple procedures. But a routine blood count showed that she was simply anemic — the horse — and just needed extra iron. The rule: Think horse without ruling out zebras.

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