The Patient Equation

1Before We Cured Scurvy

What do we know about a person? If you asked Hippocrates, he might not have that much to say. Hot or cold. Big or small. Dead or alive. Ask a physician today, and the answer is much more complex. There are thousands of medical tests we can run on a person, inside and out. Blood chemistry, urinalysis, X-rays, Dopplers, and more. We can track these results over time, in various systems, or research information online, with powerful programs like Epocrates, a medical reference app, and others. We can sequence the genome. Or we can count how many steps someone takes in a day.

Categorizing all of these observations about a person is important as we think about them as inputs to patient equations. Whether ancient or modern, these observations come with different levels of reliability and resolution. For example, movement and mood have been observed by physicians for centuries, but we can now check them digitally, reliably, and automatically—without the biases or endurance limitations of a human observer. Hippocrates could certainly count steps—but nowhere near the way a fitness tracker can.

A useful first step in our categorization comes from what most people learned in high school biology: the difference between genotype and phenotype. Before Gregor Mendel's experiments with the physical attributes of peas in the 1800s, we had little knowledge about inheritance from a medical perspective. And until James Watson and Francis Crick's famous work with DNA less ...