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(10,870 posts)
Mon Apr 20, 2020, 01:49 AM Apr 2020

Antibody Test, Seen as Key to Reopening Country, Does Not Yet Deliver

Good (layman accesible/understandable) info at NYTimes. (not behind a paywall for Covid reporting) Wish it were better news, but .. Calling it a hodge-podge is probably being kind.


-snip -- In recent weeks, the United States has seen the first rollout of blood tests for coronavirus antibodies, widely heralded as crucial tools to assess the reach of the pandemic in the United States, restart the economy and reintegrate society. But for all their promise, the tests — intended to signal whether people may have built immunity to the virus — are already raising alarms.
- snip -- In Laredo, officials discovered the tests they received were woefully inadequate. The local health department found them to have a reliability of about 20 percent, far from the 93 to 97 percent the company had claimed. A police investigation led to a federal seizure of the tests.
- snip -- More than 90 companies have jumped into the market since the F.D.A. eased its rules and allowed antibody tests to be sold without formal federal review or approval. -snip - Their products vary. Some test only for a transient antibody that spikes while the body is in the throes of an active infection. An antibody that peaks about four weeks after infection and typically marks longer-term immunity is a separate target. There are tests that look for both antibodies; others also look for a third involved in respiratory infections.
- snip -- Rapid tests are by far the easiest to administer. But they are also the most unreliable — so much so that the World Health Organization recommends against their use. Most are manufactured in China. Reports of countries that quickly bought millions have just as swiftly been followed by accounts of poor performance. For example, Britain recently said the millions of rapid tests it had ordered from China were not sensitive enough to detect antibodies except in people who were severely ill. In Spain, the testing push turned into a fiasco last month after the initial batch of kits it received had an accuracy of 30 percent, rather than the advertised 80 percent.
- snip -- In an effort to speed up access, the F.D.A. apparently did not fully consider how these tests would be administered. The agency released a guidance document saying that antibody tests could be performed at “point-of-care” settings, indicating that doctors, nurses and others could give them to patients in their offices. But agency officials also acknowledged that under federal law, if a test has not been authorized by the agency, it must be conducted in so-called high-complexity laboratories, like some large commercial facilities or public health labs. The officials decline to provide additional clarification.

- snip -- Less than 5 percent of the U.S. population may be infected, and even in hot zones like New York or New Orleans, the prevalence may not be higher than 10 to 15 percent, according to Dr. Osterholm. In China, early screening in hard-hit Wuhan indicates that only about 3 percent of the population has antibodies against the new coronavirus.
-- When the proportion of people exposed is that low, the tests’ false positive rate — signaling antibodies where there are none — can limit the tests’ utility.
-- Even Cellex’s F.D.A.-authorized test has a false positive rate of about 5 percent. That is still a significant margin of error: In a community where 5 percent of people have had the virus, Dr. Osterholm said, there would be as many false positives as true ones.

The good news .. tests are (finally) becoming more available .. in some situations, and in some places.
The not so good news .. they're mostly a mess, and they're likely not really giving us the information we need.
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Antibody Test, Seen as Key to Reopening Country, Does Not Yet Deliver (Original Post) stopdiggin Apr 2020 OP
An antibody test MAY be useful in determining who's had the illness... regnaD kciN Apr 2020 #1

regnaD kciN

(26,022 posts)
1. An antibody test MAY be useful in determining who's had the illness...
Mon Apr 20, 2020, 02:41 AM
Apr 2020

...but, since we still don't have any idea how long immunity lasts, it can't really help all that much for future planning. It would be nice if everyone who survived COVID-19 had a lifetime immunity from the disease, but that's unlikely. It's in the same variety of viruses as the common cold, and how many times have you come down with a second cold weeks after recovering from a first one?

In the long run, only a vaccine will make a full "return to normal" possible.

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