Originally published at: https://boingboing.net/2020/03/20/fda-gives-go-ahead-to-maryland.html
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Can they get like 350 million of them built, say by next Friday. Asking for all Americans.
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For this situation, you want a very low rate of false negative results, even at the cost of an annoyingly high rate of false positive results.
False positive results in unnecessary quarantine, but it’s not as if we’re going to throw you in the hospital. Go home, stay there two weeks, call if you need something.
False negatives mean more infections.
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Note that this is different from typical tests in that it isn’t looking for the virus itself – it is looking to see if the subject has antibodies to the virus. Which means that it would also be positive if somebody had the virus at one point but recovered. From the press release they do mention looking for both IgM and IgG antibodies, and IgM is more present during early infection, so maybe by doing a ratio they can determine the stage of the infection and whether it is likely cleared.
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This will be particularly useful for people who don’t know if they have already had it or not, which seems to be a worrying high percentage of people. People who were asymptomatic and light cases (which is a lot of people) who knew they had already had it - if it turns out you can’t get it twice- would be able to help out others a lot.
If I knew I had already had a light case and couldn’t get it again- and can’t pass it to others- I’d be more likely to be willing to volunteer to help deliver food to people who haven’t gotten it or whatever.
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Also, we need the blood of those that have recovered for immunization research.
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Peter Thiel calls dibs on the young ones!
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there has been some argument this company is cleverly wording their press release and the FDA has not actually cleared them specifically
they cannot be found anywhere on the FDA website among others
also this is not a test if you’ve caught covid19 but rather if you’ve now developed immunity to it, it’s basically “after the case”
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IANAD - but guessing that this test would also detect people who had and then cleared COVID-19?
—ok, just read all the comments I skipped 
Wouldn’t your doing this increase the risk of passing it to someone who doesn’t have it yet?
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We obviously need more info.
If people are contagious for ever after they recover… Then we can slow the spread and save as many as we can but eventually everyone will get it.
Let’s hope you can’t spread it after you recover, or at least after a couple of weeks after you recover, even if you are exposed to it (other than surface transfers, of course).
EDIT: Nevermind
That’s true in illnesses wheevwe have a handle on timing the transitionfrom IgM to IgG as we do with mono. I am doubtful that info if established for this beast. At this point, that may be immaterial, since it is often a few weeks to get a peak in IgG and this hasn’t been around all that long, though.
I just realized the ambiguality of my phrasing which was causing the confusion. Sorry about that! Below is the sentence as I was meaning it! 
If I knew I had already had a light case that I had recovered from and was no longer contageous with and couldn’t get it again- and can’t pass it to others- I’d be more likely to be willing to volunteer to help deliver food to people who haven’t gotten it or whatever.
(Word Nerd data: In my regional version of English, illnesses are spoken of in present tense until you are well; then they are spoken of in past tense; that sentence was fine as-is for my regional dialect (with the meaning as shown in bold) but I can easily understand how in other dialects it could be ambiguous.)
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Except, this isn’t a test to see if you’re sick “right now”. It’s a test to see if “you were sick in the past”.
A false positive would be just as bad. You’ll think this person is safe, when they’re not, could catch it later, and then infect people.
A false negative would make you think you’re still vulnerable, when you’re not.
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It’s true that an antigen test (that tests for the virus itself) would be better than an antibody test (that tests for an immune response to the virus), other things being equal. But given the exponential rate of increase in new infections right now, most of the people who test positive on an antibody test right now will turn out to be currently infected, not recovered.
The point of the test is not to classify people as vulnerable or not vulnerable to infection. The point is to use the test to trace contacts and isolate the infected. Those who test negative should still be using social distancing for the duration. Those who test positive should be isolated, and then after a period of quarantine, return to social distancing for the duration like everybody else. No test result should make anyone think they are “safe” and allowed to return to normal.
You need both types of tests, exactly for those different purposes.
Just like the rate of infected people is going up exponentially, the rate of people who were infected, recover, and are no longer transmitting is going up exponentially. Just with a time lag, along with a reduction caused by the people that don’t recover.
This new test is a good step. The point is more about the error rates for positive or negative have a large impact on what it can be used for. The reasons for using the test depend on how those error rates impact achieving the goal being looked at. It’s not as simple as one error direction is better than another, since it constrains what it can be used for.
In a month or two, an after the fact test isn’t going to be useful for identifying active infections at all.
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