THREAD

ARGH. Google’s new effort shows PERILS of lab based PCR screening

Great they’re trying, BUT:

“Employees are guaranteed a [swab] within 3 days of requesting.. & results back within 2 days of lab receiving sample”

So... 6 DAYS!! from moment deciding a test is wanted

1/x
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
Rapid tests - even if less sensitive than PCR (which they are barely less sensitive for contagiousness and more specific) - are MUCH more Effective to slow spread.

FDAs continued failure to recognize test Effectiveness as important in a pandemic is causing excess deaths.

4/x
This shows how Critical Speed of results is.

Using a high (pink) or low (gray) sensitivity test at different frequencies and w results returned at 0 (rapid), 1 or 2 days, we show that as soon as results take 2 days to return, most benefits of weekly testing are lost.

5/x
So, Googles effort is terrific!

BUT this is a perfect case example of how policy, FDA and public health approaches have been driven by medical thinking about tests and NOT public health thinking.

We need tests to stop transmission, not diagnose after the fact.

6/6
Oh. Finally - it’s really not a good idea IMO to perform PCR testing on Asymptomatic people.

(BTW, this is exactly the opposite of FDAs stance and many other people who aren’t understanding tests appropriately)

Why??

7/x
It is Bc PCR stays positive for a long time. So, if you are performing Infrequent PCR testing and you are positive but entirely asymptomatic and no risk factors - then it is more likely than not that your positive test is too late. Contagiousness may be behind you.

8/x
On other hand, a rapid antigen test is positive when contagious - and does not remain positive.

with PCR for infrequent surveillance, we are likely to catch a lot of ppl late. Which is why it is good to look at the Ct value and retest in 24h if high Ct.

academic.oup.com/cid/article/71…

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More from @michaelmina_lab

24 Dec
THREAD

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.

3/24
Read 26 tweets
23 Dec
IMPORTANT:

Particularly for UK

There’s been a LOT of concern about UK rapid antigen test program.

But here, the very tweet supposed to be showing it is failing, it shows it’s working well!!

The only missed samples were all very LOW PCR RNA - EXACTLY as expected.

1/x
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
Read 5 tweets
21 Dec
@EpiEllie @mlipsitch @vivek_murthy Thanks @EpiEllie for the ?

A number of issues:

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
@EpiEllie @mlipsitch @vivek_murthy Reason FDA confuses this is b/c they can ONLY see tests as clinical medical diagnostic devices

Not as public health screening tools

This means their metrics and what they are looking for are not congruent with their intended use in this case. Which is a major problem.

3/x
Read 8 tweets
18 Dec
THREAD:

Incredible new study results for rapid antigen test by ⁦@AbbottNews⁩ BinaxNOW

In KIDS and adults; with symptoms and fully asymptomatic.

Sensitivity:
100% at Ct <25
98.6% at Ct <30

Specificity 99.4% - 100%

1/

mass.gov/doc/binaxnow-a…
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/
Read 6 tweets
18 Dec
My 94 year old Grandma (fiancé’s Grandma) was just charged... $400 for a #COVID19 test!!

F*#^ing Criminal!

Most qPCR tests cost <$10 in reagents. Add few $ for labor/equipment.

Many commercial labs charging >$50 / test are usually preying on ppl and taking advantage.
It was not any sort of special send out overnight or anything test. It was a regular test. She went and got it in person, etc.
It was not the clinical charge.

It was not part of a bigger workup.
Read 5 tweets
15 Dec
THREAD:

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...

npr.org/sections/coron…

1/10
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).

3/10
Read 12 tweets

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