50 Percent.
(aired on All Things Considered July 29, 2003)

At the beginning of the year, our medical school dean tells each new entering class, "50% of what you will learn in medical school is wrong. The problem is, we don't know what 50%."

The first time I went to an AIDS conference to talk science rather than politics, I met a charming scientist who said, "Welcome to the field!" and toasted me with genuine enthusiasm. And then he said, "Don't come to too many conferences. Maybe one or two more, and then stop. Whenever I go to these things, I wonder if anyone understands anything." This was partly disingenuous. But that kind of skepticism is what science is all about--at least, for anyone worth traveling to a scientific conference to meet.

Perhaps it is a triumph that half of what we learn in medical school will turn out to be wrong; in that it shows the pace at which biomedical science is revising and improving and overturning old ideas. But it's also upsetting. It reminds us that medicine is not perfect, that today's proud teachings are tomorrow's inadequate theories. And yet, when we are sick or we are caring for a sick person, we can't wait. We have to use the evidence in front of us. The ways we think now.

And so, our dean's opening speech was not a critique of science--far from it. Rather, he was telling us that we'd have to keep learning science throughout our careers. We still learn plenty of facts in medical school; but hopefully, we learn even better how to learn new versions of those facts. We want to grow up to be the kind of older doctors who won't be easily outpaced by our juniors as medical ways of thinking change.

Still, sitting in immunology class in medical school was disconcerting for me. It was the only field of science I knew much about before medical school, not that I knew so much. Last year, I worked with scientists who believed that big portions of the standard dogma were wrong. So in medical school, hearing various versions of the standard dogma of immunology, I imagined my friend from last year sitting next to me, us writing notes to each other. I thought of her saying, "This is nonsense. Nonsense."

But medical school isn't science school, or not exactly. We learn about scientific topics, but we are not being trained to overturn them. As one scientist turned medical student pointed out to me, "The last thing you want as a patient is cutting-edge science."

Science needs constant doubt to advance. Medicine needs safety and predictability to remain credible. And yet, medicine also needs science. After all, if 50% is wrong, we do eventually want to figure out: which 50%? And we need to remember that though forgetting facts is one way to make mistakes in medicine, being too certain about them is another.

copyright 2003 joe wright