Stop Fearing Incidental Findings | Robbie Ostrow

(Disclosure1)

We have two options for the next hundred years of healthcare:

Gather as much data as possible, and make healthcare better (and false positives less common).

Don’t – because we’re afraid that people will get scared and act unwisely when they see an incidental finding.

Doctors in popular media are lining up to say that (1) is a Bad Idea.

From the New York Times (paywall, emphasis mine):

In April, the American College of Radiology released a statement . . . expressing concern that scans could lead to “nonspecific findings” that require extensive, expensive follow-up.

In fact, that isn’t quite what the American College of Radiology said. Their statement didn’t use the word require, but instead expressed concern that scans could lead to nonspecific findings that result in extensive, expensive follow-up.

The require vs result in mixup seems like a semantic point but it’s an important one. The ACR is not saying that follow-ups are necessary, only that they are common. These often spurious, dangerous, and expensive follow-ups are a symptom of broken processes in healthcare, not a predetermined consequence of an untargeted MRI.

More data is better

“If you scan more, you see more” is certainly true. But “if you see more, you do dangerous invasive follow-ups” doesn’t have to be. Unless we change the culture from “if you see something incidental, you must act” to “if you see something incidental, you must act if the disease is likelier to harm2 you than the follow-up,” we’ll be stuck fearing incidental findings forever.

As a bonus, by gathering more data about you, we can regularly update our priors about whether each disease is likely to cause harm.

There’s no Platonic ideal of a human body. Instead of comparing your body to some ideal from which it will always deviate, we should be comparing it<br>against your baseline. If you see something suspicious – but it hasn’t changed from your last scan – it’s likely not suspicious after all. If we do it right, more scanning should decrease the number of false positives, not increase them – but only if we’re good about not panicking when we see something outside of the “normal” range the first time we measure it3.

Philosophical point taken, but if I test positive for something, I’m still going to get the follow-up!

I’m certainly not arguing that everyone should get all of the tests all of the time (yet). They cost money and resources,<br>and because medicine is so intervention-focused today, if you get a test, your doctors may very well feel compelled to act on it – if only to protect themselves from a lawsuit4.

But we should be working to change that. We should be working to make each piece of data as cheap and safe5 as possible to gather,<br>and we should measure baselines to rule out items of concern that haven’t changed from exam to exam. We should be working to make healthcare more data-driven and less likely to skip straight to dangerous interventions. We should also be working to stop treating every piece of data as a binary “positive” or “negative” result and avoid punishing doctors for making the right statistical decisions.

Nikhil Krishnan has a great piece on why we don’t screen healthy people to catch diseases early. Cribbing directly from that piece (which is worth a read), let’s consider the extreme example of Nikhilitis, a disease that affects 1/1000 people. We have a cheap screen that is safe and 99% sensitive (if you have it, the test will be positive 99% of the time) and 90% specific (if you don’t have it, the test will be negative 90% of the time).

This means that if a random member of the population tests positive, they have a 1% chance of having Nikhilitis (math in footnote6). Subsequent health decisions should be based on that number, not on the scary word “positive.”

Let’s also imagine that the confirmatory diagnosis is a lobotomy with a 0.1% mortality rate. If the expected mortality rate of Nikhilitis is less than 10%, don’t get the freaking lobotomy! (The same footnote6 goes on to explain your expected mortality rate via confirmatory biopsy vs Nikhilitis.) But, if you’re in a special population where Nikhilitis is especially dangerous, the lobotomy might be the right choice.

Even Nikhil, whose post is otherwise excellent, implies that everyone who tests positive needs a biopsy. They don’t need a biopsy. The screen cannot ever tell you directly whether or not to get a biopsy; it just gives you more information about your risk for Nikhilitis. You only need a biopsy if that new information (plus other information about you) indicates that you’re safer to get the lobotomy than to let the possibility of Nikhilitis ride.

So if no one should get the follow-up, what was the point of the screen anyway?

Unlike the Nikhilitis screen, baseline measurements like blood panels or full-body MRIs have utility outside of a binary decision on a specific day. If you get a full-body MRI, you...