Every test has risks. There are risks of false positives and false negatives. For example, a false positive is when an HIV test says you have HIV, but you really don’t. And a false negative is when the HIV test says you don’t have HIV, but you really do. Every test that doctors perform have very well-described false negative and false positive rates.

Tests come in all kinds of different flavors from blood tests and x-rays to physical exams. Anything that generates some sort of data can be considered a test. Zeke Emanuel recently wrote in the New York Times that we should skip our annual physical exam because it’s simply a bad test:

In 2012, the Cochrane Collaboration, an international group of medical researchers who systematically review the world’s biomedical research, analyzed 14 randomized controlled trials with over 182,000 people followed for a median of nine years that sought to evaluate the benefits of routine, general health checkups — that is, visits to the physician for general health and not prompted by any particular symptom or complaint.

The unequivocal conclusion: the appointments are unlikely to be beneficial. Regardless of which screenings and tests were administered, studies of annual health exams dating from 1963 to 1999 show that the annual physicals did not reduce mortality overall or for specific causes of death from cancer or heart disease. This lack of evidence is the main reason the United States Preventive Services Task Force — an independent group of experts making evidence-based recommendations about the use of preventive services — does not have a recommendation on routine annual health checkups. The Canadian guidelines have recommended against these exams since 1979.

And here’s the kicker:

Some are actually hurt by physicals, because healthy patients who undergo an exam sometimes end up with complications and pain from further screening or confirmatory tests.

Fascinating isn’t it? Ever think that an annual physical exam could harm you? The bottom line is that it’s simply not a very good test at all. It’s too blunt a tool.

But there’s a new kind of test on the horizon. It’s called wearables. There’s a big push from the wearables industry to force some sort of wearable ubiquity upon us.

But these wearables are, in fact, tests. They are tools to generate data just like blood tests, x-rays and physical exams. Some of these data-generating tools are exceptionally helpful and some are actually harmful not only for pain and suffering, but also for initiating costly further testing. They will have false positives and false negatives. They may diagnose diseases that will never actually harm us. They may diagnose diseases that we can’t do anything about. They may provide early diagnoses and force us to live with anxiety longer than we need to.

As wearables tread ever closer to tracking more medical values (blood glucose) instead of health values (steps taken), they may actually do more harm than good and we should be open to this possibility. Everybody thought that physical exams were helpful. They’re not and they may be harmful. We might find ourselves in the same predicament with wearables triggering further unnecessary and costly testing. I’m not saying it’s probable, just that it’s possible.