Your positive virus antibody test probably doesn’t mean you’re safe



I’m sure you wanted to kick off your Wednesday morning with some great news, but I’m afraid this isn’t it. As you likely know by now, the big debate raging in Washington and all across the country at the moment is over the question of whether we’re “testing enough” to pin down the spread of the novel coronavirus. The President says we are. Speaker Pelosi says we aren’t. That’s just politics as usual and you could insert virtually any other topic of debate in place of the virus and get the same result.

But as we rush to test as many people as possible, is that really getting us anywhere? On a more personal note, if you sign up to be tested for antibodies and get a positive result, an indication that you’ve already been exposed to the virus, does that mean that you’re good to go about your normal life because you are now immune? This report at CNN suggests that all of this testing may not really be proving anything. In fact, until we know a lot more about this virus and get hard data on the efficacy of the tests being used, we really can’t draw any conclusion.

In today’s reality, testing positive for antibodies to Covid-19 means nothing of the sort. In fact, it may not mean much at all — at least right now.

There are still too many unknowns, both about the accuracy of the antibody tests that are available and about the nature of the virus itself.

“It is clear that we’re still not where we need to be. It’s a brutal truth, but one that needs to be told,” said CNN Chief Medical Correspondent Dr. Sanjay Gupta in the May 5 episode of his podcast, called “Coronavirus: Fact vs. Fiction.”

“And this is exactly why I keep advising people to behave like you have the virus,” Gupta said.

While much of this is new to me, we’re definitely seeing something very different than the way most of us thought about the concept of vaccines in the past. Traditionally, if you were vaccinated against a disease, you had a reasonable expectation that you wouldn’t catch it. Similarly, if you contracted a particular disease and survived it (think of chickenpox back in the day), that also conferred immunity on you and you were good to go.

But the coronavirus is still far too new and too many unknowns remain. First of all, the tests being used are coming from a wide variety of sources and not all are of equal quality and accuracy. A recent study of five commonly used diagnostic tests performed at the Cleveland Clinic found 15% of them delivering false negatives. A separate study done in China found the error rate to be 40%. That’s closing in on 50%, at which point you’d have just as much luck flipping a coin as going down to the clinic to be tested.

The report also indicates that some of the newer antigen diagnostic tests are nowhere near sensitive enough. If you were only recently infected, the tests frequently deliver a negative result because your body hasn’t had time to build up a sufficient volume of antigens. So you could test negative today and still come down with the disease the following week even if you’re locked up in your house like a hermit.

And finally, the presence of antibodies in your blood means that you have been exposed to the virus. But sadly, it doesn’t mean that you are immune. The report lists a few possible explanations for this, but it sort of shoots a hole in the entire “herd immunity” theory if it’s true. One big potential problem, as Karen reported last night, is that the virus appears to be continually mutating. There are potentially as many as four distinct strains going around including the original one from China and others that mutated when they landed and spread in Europe, Africa, and South America before arriving on our shores. Being “immune” to one of them doesn’t necessarily mean that you’re immune to all of them.

I’m not trying to play Debby Downer this morning, nor do I think we need to needlessly delay reopening the country for business. But as we continue to gather data on this pandemic, it seems foolish for people to completely disregard the safety precautions we’re currently taking as they go about their business. And now, that even applies to those who had the disease and recovered.





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