I probably get more questions about COVID-19 testing than anything else these days.
And it’s really no wonder… All we hear about is testing, testing, testing. Which is understandable, to an extent—but, as I recently explained, it’s not the way out of this global crisis. (At least, not given the limitations of the testing we have now.)
So I’d like to kick off today’s discussion by offering up my favorite headline of the week: COVID ‘Immunity Passport’ No More Reliable Than a Coin Flip.
Welcome to the wild west
We all want to know if we have been infected. We all want to know if we are immune. And it would be great if any of the tests we currently have could accurately give you the confidence you may need to get back to work, get back on a plane, or to feel safe visiting an older relative.
But, let me stress this once again: We do not have these answers.
Just because a test shows that you have antibodies against the novel coronavirus, it doesn’t mean that you have protective antibodies. You would need a specialized viral culture to confirm that.
Let me also remind you that most of the tests on the market have been exempt from Food and Drug Administration (FDA) review, which means it’s basically the wild west out there. Pretty soon, you’ll be able to get tested on every corner—if we’re ever allowed outside again—and results will only be that much harder to verify.
If you’ve been following along with these COVID-19 conversations, then you’re already aware of all of this. But unfortunately, the issue still isn’t getting the lip service it needs to ensure that the public has a clear understanding of what’s at stake.
If we rely too heavily on testing to make decisions, we risk some pretty grave missteps. And here’s why: A positive antibody test, in many cases, only offers a 50/50 chance of accuracy.
That’s right—the same as a coin flip.
Heads or tails?
Here’s a quick example for you. Let’s say you have a town of 100,000 people. Now imagine that 5 percent have been infected with COVID-19 and survived with protective antibodies. That would mean that 5,000 people are immune.
Now, let’s imagine we test everyone to see who has antibodies. (I’m going to assume the test is 100 percent sensitive, just to make the math simple—but you should know that NO test is ever 100 percent sensitive.) That means the test will identify those 5,000 people.
But now, let’s say the test is only 95 percent specific (which means you get a 5 percent false positive rate—still not too shabby). That means that 5 percent of the 95,000 who aren’t immune—some 4,750 people—will also test positive.
So now we have 9,750 people who tested positive… but of which only 5,000 are actually immune. As you can see, that is a “positive predictive value” of around 49 percent. In other words, this test is the same as a coin toss.
The only way such unreliable testing can improve in accuracy is when the number of symptom-free antibody carriers rise above a certain key percentage. (NYC may be there by now… but the country as a whole certainly isn’t.)
And the problem is that misunderstandings about these tests’ accuracy rates have the potential to seriously endanger people—especially with more populations looking at antibody testing as a way to “reopen.”
Bottom line: If your city or town has an infection rate below 20 percent, no positive antibody test currently available is going to serve as a free pass to resume business as usual. And you drop your previous precautions at your own—and your community’s—very real risk.
Now, if you know you’ve had COVID-19, and you have since recovered, then a positive antibody tests probably does mean that you’re protected. But even then, we really don’t know for sure. Not yet, at least.
There’s still so much to learn—and still too much fear-mongering going around. So as always, I urge you to stick around as I try to make sense of it for you and for myself.
And tomorrow, I’d like to dive into another key player in our lives after coronavirus: vaccines. So, stay tuned…
P.S. Even with so much uncertainty surrounding testing and immunity to COVID-19, as always, there are numerous ways you can support, balance, and boost your immune system—naturally. In fact, I outline my top immune health recommendations in my Complete Guide to Year-Round Immunity. To order yourself a copy today, click here now!
“COVID “Immunity Passport” No More Reliable Than a Coin Flip.” Medscape Medical News, 05/27/2020. (medscape.com/viewarticle/931097)