NEW! research shows rapid antigen tests can work in a real world setting - with asymptomatic and symptomatic people. The rapid "paper-strip" antigen test called the BinaxNOW detected >90% of people with high viral loads who are likely to be infectious…

I've written about the BinaxNOW from @abbottnews before and why these types of tests can be 'game changers' for our ability to combat this virus

As expected... the BinaxNOW did NOT detect all PCR positive people... only ~60%

BUT DID detect >90% of those with high/contagious virus load. THESE ARE THE PPL THAT MATTER most when trying to cut off transmission chains.

If goal is to detect ppl who are likely contagious, PCR can be too sensitive. Many - or MOST PCR positve ppl who are detected through infrequent surveillance testing are no longer infectious by the time they are detected

This issue that PCR positivity does not equal infectious positivity was also well reported in a recent @nytimes article also by @apoorva_nyc that has really raised awareness of why we MUST consider PCR Ct values.…

Back to the new research.. the BinaxNOW rapid test was able to detect most (93%) ppl with high viral loads - consistent with cultural positive/potentially transmissible virus. The BinaxNOW did not capture PCR positive people with low RNA copy numbers unlikely to be contagious

If the goal is to find infectious people, this is OK... or perhaps even better so that we are not isolating people who are no longer infectious. Again, covered in this article. (which admittedly caused some confusion)…
Some say "we don't know enough" yet about Ct values & transmission-but we do.

Even forgetting how much we knew PRE-COVID on this issue, numerous #COVID19 studies show strong correlation where high PCR Ct values are culture neg:…

Importantly, the above study also found essentially no culture positive samples >10 days past symptom onset - regardless of Ct value. Rapid antigen tests would mostly be neg at >10 days and thus can be MORE accurate for detecting contagious people than PCR...

This new BinaxNOW data from SF shows that rapid paper strip tests can work very well to detect potentially infectious people, with >90% sensitivity....

Importantly, even when the overall sensitivity against PCR is only 50%!

This point cannot be overstated... PCR positivity is not the right benchmark if the goal is detection of infectious people!

Please let us stop using simply PCR "positive/negative" as the benchmark - we CAN be more nuanced.

Two additional papers have come out recently that further enforce rapid tests...

One looking at BD rapid test which, like BinaxNOW showed that a rapid test is potentially MORE accurate than PCR if the goal is detection of contagious virus.

An additional important study just came out as well from @MarionKoopmans lab that not only showed that rapid antigen tests can be very accurate to detect culturable virus - but importantly shows that not all rapid tests are equal

In that study, they found that some rapid tests: another rapid test from Abbott 'PanBio' and the SD Biosensor rapid test performed exceptionally well against high virus. While other tests performed quite poorly.

Still though, even the poorest tests in that study, one by Rapigen, performed with >70% sensitivity and thus could still have a role in identifying many contagious people.

To conclude, the evidence is mounting for the role of rapid antigen tests.

These tests work to identify infectious people quickly, without delay. They are best used to identify infectious people when they are used frequently:…
We layed out the science behind their use to control outbreaks here, with @DanLarremore , @jameshay218 @brwilder @MilindTambe_AI, Roy Parker and others…

And for any policy makers out there @alexismadrigal covered the "big idea" of how rapid tests can be used to control outbreaks here:…

We don't need to test every person every day, just a fraction, every few days, in places where outbreaks are the worst to get them under control quickly and make everyone more safe

We don't have a vaccine yet. We might not for a while. Frequent rapid testing can work

FYI Some of the confusion is that these aren’t actually false positives. also I do not call for any universal cutoff from pcr values to say someone is not infectious. But I would say that below certain Cts people are very like to be infectious. Above, we should be more nuanced.

• • •

Missing some Tweet in this thread? You can try to force a refresh

Keep Current with Michael Mina

Michael Mina Profile picture

Stay in touch and get notified when new unrolls are available from this author!

Read all threads

This Thread may be Removed Anytime!


Twitter may remove this content at anytime! Save it as PDF for later use!

Try unrolling a thread yourself!

how to unroll video
  1. Follow @ThreadReaderApp to mention us!

  2. From a Twitter thread mention us with a keyword "unroll"
@threadreaderapp unroll

Practice here first or read more on our help page!

More from @michaelmina_lab

14 Oct
Rapid test data!

@MarionKoopmans and team evaluate rapid “paper-strip” Ag tests against likely contagious virus samples

Here @AbbottNews PanBio and SD Biosensor rapid tests perform very well to detect infectious virus

But, not all tests are equal…
1/ Image
The authors evaluated a number of different tests against PCR positive and culture positive specimens. (Culture positive is generally appreciated as representing likely transmissible virus).

They find a large disparity across different tests...

Against culturable virus, they find that the Abbott PanBio Test and the SD Biosensor (Neither available in the US right now) perform very well. An additional 3 tests were evaluated 2, also looked quoted good but the rapigen performed quite poorly.

Read 4 tweets
14 Oct
New research! Starring... Ct values!

We endeavored to ask:

Can we create a brand new metric to know if #COVID19 is increasing/decreasing without staring at case counts & fractions positive - both greatly obscured by test practices.

Yes! w/ Ct values!…
In this incredible Tweet thread 👆 @jameshay218 describes the new work - we hope will lay new groundwork for public health authorities to track this/future viruses & if control strategies are working

Work also w co 1st author Lee Kennedy-Shaffer, @mlipsitch & @SanjatKanjilal
One piece that is so cool about this method is we do NOT need a time series of case data to create a trajectory (those little bars on @nytimes website or google that we’ve all stared at for the past 9 months to see trend up vs down in cases). We can do it from a single day!

Read 7 tweets
13 Oct

This virus is not happening in a vacuum where no information existed previously

On Immunity, On testing, On serology, On transmission, On masks, On treatments...

We must stop this narrative that we know nothing of this virus until we learn it anew - again.

The constant drum beat of “we do not know that yet” is tiring.

We KNOW SO MUCH! about SARS-CoV-2 and COVID-19. We knew it before this virus was ever discovered!

We’ve watched since January with study after study reaffirming out expectations of this virus in SO MANY WAYS.

In many we ways we got lucky on this front.

Take HIV for ex. HIV was a new virus for which we generally did have to rewrite the text book

But this virus is different from HIV in that it is behaving in almost all ways per the “textbook”.

Read 19 tweets
13 Oct
So important in this pandemic to NOT let RARE events make the headlines & grab our attention

@NPR - this should NOT be a headline unless you’re going to have daily headlines that say “Millions NOT reinfected today with COVID19”

People are scare enough…
Re-exposures are essential to build our immune system. This is not in question. They are like training.

But like anything, when enough people get a re-exposure, there are going to be rare cases here and there that go awry and someone gets more sick the second time.

But this is rare and should NOT be interpreted as people will not build protective immunity and that vaccines will not work.

The take away from this piece should be “In a rare event, a person in the US gets a severe second infection with SARS-CoV-2”

One other point

Read 7 tweets
12 Oct
Trump tested negative on @AbbottNews BinaxNOW test. His MDs are using for evidence of no longer contagious

I don’t disagree - but like use of tests to stop transmission - this is just one piece. Frankly, in this context, it’s being used out of context...

The most important point of deployable rapid tests are that they can be used by many people, frequently!

But should not be used as confirmatory testing of -ve PCRs. This doesn’t make sense and WH use for this confuses how these tests are most appropriately used.

These tests should be to screen ppl (frequently) for +ve results to identify people likely needing to be isolated

In this case @POTUS has had numerous PCR tests and is the president! He can get a viral culture test if he wants to go out w confidence he is not contagious

Read 5 tweets
10 Oct
IDNOW by @AbbottNews rapid test is what @POTUS uses

It's said to be poor w very low sensitivity - the news, @US_FDA and many others say so

But this is a mistake. It's a very good rapid test

I explain here at ~3:30
(Just found link from an old talk)

The short story is the main study from NYU that led to the low sensitivity claims used an extremely skewed sample set

If you remove from the paper just the +ve samples with a Ct value >40 (incredibly miniscule RNA loads), the sensitivity of the test jumps from 60% --> 90%!
If you take only samples with Ct values <38 (still on par w almost any other PCR test), then sensitivity jumps from 60% --> 95%!!

So the problem wasn't the test, it was the samples evaluated. 30% of them were at the very limit of detection of a SLIGHTLY better test
Read 6 tweets

Did Thread Reader help you today?

Support us! We are indie developers!

This site is made by just two indie developers on a laptop doing marketing, support and development! Read more about the story.

Become a Premium Member ($3/month or $30/year) and get exclusive features!

Become Premium

Too expensive? Make a small donation by buying us coffee ($5) or help with server cost ($10)

Donate via Paypal Become our Patreon

Thank you for your support!

Follow Us on Twitter!