In its most basic sense, the physical exam is a method of inferring the state of health of the internal organs. For two centuries, it has been accomplished through auscultation, inspection, palpation, and percussion.

These techniques complement the taking of a detailed history, designed to flesh out uncertainties arising from the patient’s subjective report.

However, such methods are often so imprecise that they do little to reduce uncertainty or narrow our differential diagnosis at all.

Consider the diagnosis of congestive heart failure (CHF), one of the most common causes of hospitalization in the United States.

Since the 1800s the signs and symptoms of CHF and its downstream ramifications have been well understood.

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