The rapid antigen tests caught all of the high viral load cases that were likely contagious and missed the low RNA level cases who were most likely beyond their contagious period.
This suggests the testing was simply too infrequent to catch the important cases.
2/x
At what point are we going to stop making the claim that these tests are too insensitive?
They are doing the job exactly as anticipated. Public health is not about diagnosing and isolating old COVID cases. It’s about identifying current contagious people.
3/3
To clarify a central issue with Birmingham Rapid Antigen Test study:
The study results show that for:
Ct < 30, Sensitivity = 5%
Ct < 29, Sensitivity = 100%
Any time the sensitivity jumps from 5% to 100% in a SINGLE Ct value, you know there is a major problem with the study.
Also, in that tweet thread it mentions half the positives in a different study were false positives. Not mentioned was this was due entirely to low prevalence.
What the thread should have also mentioned in same breath was that specificity was >99.9%!! Very high specifity!
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There is (rightly) concern about the variant SARS-CoV-2 strains. I want to talk about what this means for vaccines, our future, and why we MUST have contingency plans.
This thread is in response to many questions I've received.
1/24
First, Note: I'm not doing a deep dive on specific mutations. For that, see @angie_rasmussen@jbloom_lab@K_G_Andersen@BillHanage. I am an infectious disease immunologist / epidemiologist & study viruses/vaccines. So I'll speak from that perspective.
2/24
Second Note: I do not want this thread to be alarmist.
To put it upfront, the mutations thus far do not indicate a major evasion of immunity interfering w vaccines. However, the mutations should be a wake up call to action.
That the test is being performed weekly is great. Perhaps people can order ahead. Still, with shipping, it will most likely be 3 days between the swab being used and result provided back. If it’s positive, that’s 3 days of walking around positive.
2/x
This is a good effort from Google.
But this sheds concrete light on the problems of delayed test results for an acute respiratory virus.
A 3 day wait erases ~50% of the EFFECTIVENESS of the test to stop transmission. A 6 day wait erases ~90% of the effectiveness
3/x
1) Regulatory - FDA must remove unnecessary regulatory requirements
Most crucial: ~90% sensitivity against PCR in ASYmptomatics w/out allowing a Ct cutoff
By time asymptomatics are found w PCR, Ct is >30 & post-infectious
1/x
@EpiEllie@mlipsitch@vivek_murthy By requiring demonstrating sensitivity specifically in asymptomatics, FDA is confusing EUA application with showing physiology of the virus.
Many studies show asymptomatics have virus.
The tests care about virus, not symptoms. FDA is confusing this point.
2/x
The study above, by @NiraPollock and others, is incredibly important because it proves that these tests do not care about your symptoms, they only care about the virus. And that they work in kids as well as adults.
The former issue is critically important...
2/
Currently @US_FDA requires that for these tests to be used at home OTC, they need to demonstrate explicitly that they work in asymptomatic people.
But this is completely unnecessarily burdensome - plus finding asymptomatic people shedding virus is very difficult!
3/
First at-home rapid test w FDA EUA! This is a great milestone! Congratulations to @EllumeHealth on this triumph. The EUA for this at-home test should be celebrated. I am supportive & have used it myself! I want to put this in context...
This is a terrific milestone. An OTC rapid test is a great advance. It means some will have access to much needed test to help know status, without going through barriers of an MD.
Since many are asking, this is not quite THE public health screening test I'm calling for.
2/10
Inside, @Ellume (right) has simple but powerful paper strip test. It requires battery, circuits, sensors, and bluetooth with a mobile phone. Thus, not quite THE mass public health screening test that will scale for frequent use by millions (i.e. vs simple one on left).