3 ms·

Many of the COVID tests are not cleared/approved or even authorized for emergency use yet. But, this is what we are having to rely on to count confirmed cases d

by _wldu 7y ago

Many of the COVID tests are not cleared/approved or even authorized for emergency use yet. But, this is what we are having to rely on to count confirmed cases due to the circumstances. https://www.questdiagnostics.com/dms/Documents/covid-19/SARSCoV-2_Patient_Fact_Sheet.pdf https://www.questdiagnostics.com/dms/Documents/covid-19/SARS... "Is this test FDA-approved or cleared? No. This test is not yet approved or cleared or authorized by the United States Food and Drug Administration (FDA). When there are no FDA-approved or cleared tests available, and other criteria are met, FDA can make tests available under an emergency access mechanism called an Emergency Use Authorization. Quest Diagnostics is working with FDA to obtain Emergency Use Authorization." And the tests that are authorized for emergency use are not FDA cleared or approved. "Testing was performed using the cobas(R) SARS-CoV-2 test. This test was developed and its performance characteristics determined by LabCorp Laboratories. This test has not been FDA cleared or approved. This test has been authorized by FDA under an Emergency Use Authorization (EUA). This test is only authorized for the duration of time the declaration that circumstances exist justifying the authorization of the emergency use of in vitro diagnostic tests for detection of SARS-CoV-2 virus and/or diagnosis of COVID-19 infection under section 564(b)(1) of the Act, 21 U.S.C. 360bbb-3(b)(1), unless the authorization is terminated or revoked sooner."

pmoriarty 7y ago
On the subject of unreliable tests, here's a transcript of a letter read on episode 588 of This Week in Virology[1]: I'm an infectious disease doctor and would like to point out an important factor in diagnosing this infection (and all respiratory pathogens that use nucleic acid probes for specimen collection). This is of particular concern now that China has transitioned to a much more problematic clinical diagnosis based more on clinical symptoms than PCR testing. While it may seem trivial how a health care worker jams a swab in to someone's throat or nose, technique is important. If anterior naries (front of nose) swabs or side of mouth swabs are done, rather than the true posterior nasopharynx or oropharangeal swabs, the sensitivity drops dramatically. We have shown this to be true repeatedly with diagnosis of influenza and respiratory pathogens, and I am disappointed that it has not been mentioned more in discussions about the PCR tests, missing the diagnosis in people who are positive and negative then positive again. We often see people admitted from the ER with the perhaps carelessly collected flu test who miraculously are flu positive by the time they are admitted. Like so many cultures and diagnostics in infectious diseases, specimen collection and handling is critical. I warn my patients about the unpleasantness of a nasopharangeal swab and jokingly tell them that if it doesn't cause a wincy-face reaction we haven't collected specimens from where the viruses reside. [1] - http://www.microbe.tv/twiv/twiv-588/; http://www.microbe.tv/twiv/twiv-588/; at about 1 hour and 38 minutes in
- macintux 7y ago
  I had one of those nasopharyngeal swab tests conducted about a month ago for the flu. It was extremely unpleasant, so I can concur with the good doctor, albeit astonishingly brief.
icegreentea2 7y ago
The EUA-ness of the test has very little to do with re-positives. RT-PCR tests can only test for the presence of viral RNA in the sample collected. They cannot tell you the viability of the viral particles, they cannot tell you if you going to get sicker, or going to get better the next day. We don't even fully understand the relationship between vRNA detection and contagiousness. And all of those unknowns are outside of the scope of the test. Even in normal times, these tests can only be used to determine if genetic material exists (and sometimes the quantity if the collection mechanism and processing are controlled enough). It must be left up to clinicians to interpret these results. The current protocol is to wait for 2 consecutive negatives 24 hours apart to call someone virus free. That's a protocol created by clinicians in a time of extreme pressure and need based on empirical measurements and prior body of knowledge. A 510k cleared COVID test would have most of the same issues because the problem isn't strictly that the tests can't reliability detect viral particles, the problem is that we don't know what actually constitutes "cured".
- _wldu 7y ago
  Right. The point is that due to testing issues (false negatives at 33%[1], not done properly, etc.) a positive test result after a negative result (when COVID symptoms are present) is not a sign of re-infection or relapse but an indicator of testing problems/issues. [1] https://www.wsj.com/articles/questions-about-accuracy-of-coronavirus-tests-sow-worry-11585836001?mod=e2tw https://www.wsj.com/articles/questions-about-accuracy-of-cor...
  - icegreentea2 7y ago
    Yeah, it's a huge problem. But I think its also very important to be precise about it. Careless phrasing about test kit performance can make people think that the problem is that our test kits "just need to be better". These test kits can have fantastic sensitivity when measured on a per sample basis, and absolutely awful clinical sensitivity at the same time. We're incredibly unlikely to get significantly better clinical sensitivity, especially for tests appropiate for population level screening over any reasonable time frame, so our strategies and plans are going to have to accommodate that.

by _wldu 7y ago

pmoriarty 7y ago

On the subject of unreliable tests, here's a transcript of a letter read on episode 588 of This Week in Virology[1]: I'm an infectious disease doctor and would like to point out an important factor in diagnosing this infection (and all respiratory pathogens that use nucleic acid probes for specimen collection). This is of particular concern now that China has transitioned to a much more problematic clinical diagnosis based more on clinical symptoms than PCR testing. While it may seem trivial how a health care worker jams a swab in to someone's throat or nose, technique is important. If anterior naries (front of nose) swabs or side of mouth swabs are done, rather than the true posterior nasopharynx or oropharangeal swabs, the sensitivity drops dramatically. We have shown this to be true repeatedly with diagnosis of influenza and respiratory pathogens, and I am disappointed that it has not been mentioned more in discussions about the PCR tests, missing the diagnosis in people who are positive and negative then positive again. We often see people admitted from the ER with the perhaps carelessly collected flu test who miraculously are flu positive by the time they are admitted. Like so many cultures and diagnostics in infectious diseases, specimen collection and handling is critical. I warn my patients about the unpleasantness of a nasopharangeal swab and jokingly tell them that if it doesn't cause a wincy-face reaction we haven't collected specimens from where the viruses reside. [1] - http://www.microbe.tv/twiv/twiv-588/; http://www.microbe.tv/twiv/twiv-588/; at about 1 hour and 38 minutes in

macintux 7y ago
I had one of those nasopharyngeal swab tests conducted about a month ago for the flu. It was extremely unpleasant, so I can concur with the good doctor, albeit astonishingly brief.

icegreentea2 7y ago

The EUA-ness of the test has very little to do with re-positives. RT-PCR tests can only test for the presence of viral RNA in the sample collected. They cannot tell you the viability of the viral particles, they cannot tell you if you going to get sicker, or going to get better the next day. We don't even fully understand the relationship between vRNA detection and contagiousness. And all of those unknowns are outside of the scope of the test. Even in normal times, these tests can only be used to determine if genetic material exists (and sometimes the quantity if the collection mechanism and processing are controlled enough). It must be left up to clinicians to interpret these results. The current protocol is to wait for 2 consecutive negatives 24 hours apart to call someone virus free. That's a protocol created by clinicians in a time of extreme pressure and need based on empirical measurements and prior body of knowledge. A 510k cleared COVID test would have most of the same issues because the problem isn't strictly that the tests can't reliability detect viral particles, the problem is that we don't know what actually constitutes "cured".

_wldu 7y ago
Right. The point is that due to testing issues (false negatives at 33%[1], not done properly, etc.) a positive test result after a negative result (when COVID symptoms are present) is not a sign of re-infection or relapse but an indicator of testing problems/issues. [1] https://www.wsj.com/articles/questions-about-accuracy-of-coronavirus-tests-sow-worry-11585836001?mod=e2tw https://www.wsj.com/articles/questions-about-accuracy-of-cor...
- icegreentea2 7y ago
  Yeah, it's a huge problem. But I think its also very important to be precise about it. Careless phrasing about test kit performance can make people think that the problem is that our test kits "just need to be better". These test kits can have fantastic sensitivity when measured on a per sample basis, and absolutely awful clinical sensitivity at the same time. We're incredibly unlikely to get significantly better clinical sensitivity, especially for tests appropiate for population level screening over any reasonable time frame, so our strategies and plans are going to have to accommodate that.