Why every screening test is a gamble

I'm in Las Vegas for the first time in 15 years to attend the International Consumer Electronics Show, and earlier today participated in a panel of "early-adopter" family physicians discussing our perspectives on consumer (patient) health technology such as apps and wearable health data collection devices. I'm staying at one of Vegas's many combination hotel and casinos, with a layout designed to funnel guests and other visitors through the gaming floor to get practically anywhere. While walking past a row of pulsating slot machines in the lobby this morning, I remembered the title of a terrific New York Times editorial I read a few years ago, "You Have to Gamble On Your Health."

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In this editorial, Dr. H. Gilbert Welch (whom I've lauded before for his work on the subject of overdiagnosis) explained why even though most people who receive screening tests for cancer think that they are playing it safe, every test has tradeoffs. Just as a gambler rarely hits the jackpot in Vegas, a patient who undergoes cancer screening is rarely the lucky one whose life is extended from the test, and much more likely to figuratively lose his or her shirt. Common harms of screening include false positive results, risks associated with subsequent diagnostic procedures, and possible unnecessary treatment (and associated side effects) for "cancer" that looks dangerous under the microscope but is actually destined to never cause health problems.

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The good news is that for a few very well-studied screening tests such as mammography, an informed patient can assess the odds of all of these outcomes and decide whether screening is a better choice for her than no screening. A mammography screening decision aid by Dr. Jill Jin that appeared in last month's JAMA did a great job of illustrating these tradeoffs, and may help to explain why a prominent health journalist recently announced that she had decided to forego mammography because she believed that "the numbers are in my favor."

Yes, every screening test is a gamble, but I give credit to my fellow physicians for providing increasingly sophisticated support for these tough decisions that you'd never get in Vegas.