We don't go to chemists and ask for legal counsel. We don't go to hairdressers to talk about the mechanics of our cars. Yet when it comes to our bodies, we routinely take medical advice from just about any "expert" — actor or folk singer, health-store owner or sports hero.



Most recently, the billionaire business tycoon (and Dallas Mavericks owner) Mark Cuban stepped into the position of health-care adviser, giving his nearly 3 million Twitter followers guidance on how often they should get their blood tested.

1)If you can afford to have your blood tested for everything available, do it quarterly so you have a baseline of your own personal health — Mark Cuban (@mcuban) April 1, 2015

2) create your own personal health profile and history.It will help you and create a base of knowledge for your children,their children, etc — Mark Cuban (@mcuban) April 1, 2015

3) a big failing of medicine = we wait till we are sick to have our blood tested and compare the results to "comparable demographics" — Mark Cuban (@mcuban) April 1, 2015

Very quickly, evidence-based medical tweeters seized on Cuban's health advice.

I don't get why @mcuban thinks we should get labs quarterly. If more data=better, why not daily? @ddiamond @charlesornstein @BrendanNyhan — Aaron E. Carroll (@aaronecarroll) April 2, 2015

Please don't listen to @mcuban advice to get quarterly bloodwork if you are healthy. https://t.co/gxV1UMMxUU — Charles Ornstein (@charlesornstein) April 1, 2015

@mcuban @charlesornstein well no doctor I know gets regular blood tests to capture data — Jennifer Gunter (@DrJenGunter) April 2, 2015

@charlesornstein @mcuban Testing for the sake of testing very bad medicine. — Yoni Freedhoff, MD (@YoniFreedhoff) April 1, 2015

Charlie Ornstein, a Pulitzer Prize–winning health reporter at ProPublica, captured his tussle with Cuban in this entertaining Storify. He zeroes in on exactly why Cuban's advice is absurd: more health care isn't necessarily better health care, and recreational testing can send people into costly and unhelpful cascades of care.



In particular, Ornstein quotes Dr. H. Gilbert Welch, author of Overdiagnosed: Making People Sick in the Pursuit of Health:

But the truth is there are really two sides to the story. I think patients are used to thinking of treatments as having side effects, but so does testing. And the side effect of looking for early forms of disease is that we find, virtually, all of us have some. That's because we all harbor some abnormalities. And we never know which patients are those that have abnormalities that are going to cause problems in the future. So we tend to treat everybody we find with an abnormality and that means we're just treating some patients who can't benefit from our treatment because they were never going to develop the problem at hand if they're overdiagnosed.

Aaron E. Carroll, a professor and health researcher, went into some detail about the trouble with Cuban's logic in a post at the Incidental Economist blog.

"First of all, people presume that tests are binary things," Carroll writes. "They're not. When you get a blood test, it doesn't come back 'sick' or 'well.' It comes back with a number value."

What that number means isn't always clear — and tests can be wrong, turning up "false positives." When there's no indication for the test, patients can subject themselves to unnecessary stress and worry. Or as Carroll puts it: "This is why I teach residents and medical students never, ever to order blood tests unless they are looking for a specific problem."



Unfortunately, it's not clear how many may have been affected by Cuban's bogus health advice and whether any of this sensible counter-messaging will get through.