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053: Why more testing from Theranos won’t prevent cancer

It’s a compelling promise: take a few drops of blood, and tell the patient what hidden diseases are lurking in his body.  If only we could have an early warning system for cancer, Alzheimer’s, or myriad other diseases, then we could treat them before they took hold.

This is the narrative of Theranos, a company that wants to make medical testing affordable and fast for everyone.  They’ve taken the notion so far that they actually publish a price list for hundreds of tests right on their website.theranos price list

Recently, the company made less favorable headlines when the Wall Street Journal revealed that many of the tests were performed on industry standard equipment, rather than the space-age technology Theranos markets.

The company’s troubles deepened when federal regulators announced plans to revoke the license of one of its lab facilities and to ban CEO and founder Elizabeth Holmes from the industry for two years.

But technology and regulations aside, there’s a more fundamental question we should all be asking: is wider access to routine screening a good thing?

The math says no.

Damn Lies and Statistics

This week on the show, we discuss a recent article from that makes a bold claim: “We don’t need more blood tests.”  The reason comes down to some counterintuitive probabilities.

Fundamentally, the value of routine screening for rare diseases comes down to just a few numbers: the sensitivity of our test, the specificity of our test, and the prevalence, or rareness, of the disease we’re trying to detect.

Even if sensitivity and specificity are high, they can lead to unintended consequences when we screen truly large numbers of people.  We walk through an example on this week’s episode with a made-up test and a made-up disease.

But the impact of broad scale screening is very real.  In fact, the recommendations for routine mammography and breast cancer screening have been changed recently due to the outsized side-effects of false positives in the screen.

There’s value to testing, but we have to make every effort to test the right people at the right time, and to help them interpret their results.  Our intuition is not always a helpful guide.

This Beer is Hot Hot Hot

This week, we turn up the heat with a Habanero IPA from Dingo Dog Brewing in Carrboro, NC.  Dingo Dog grows some of its own ingredients onsite in a “zero waste” production facility, and they use the profits to fund grants to local, “no-kill,” animal rescue organizations.

Their mission is cool, but this beer is hot!  It’s got all the bitterness you love in an IPA with a little kick of spice on the back of the throat.  Keep another brew on hand as a chaser!


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