The extra $1B towards purchasing rapid tests is a great step forward. It is a strong signal that the WH and the Federal government is recognizing that American's are demanding to be able to know if they are infectious in real time.
So I'm fully supportive of the WH support
A question was just asked to @CDCDirector about whether roll out of rapid tests will limit the public health reporting
This is an important question and a good reason the federal government should simultaneously prop up efforts to make these tests verifiable and reported.
In many parts of world, rapid testing is commonplace. Policymakers recognized early that rapid tests could blunt the pandemic by scuttling transmission chains. They created special regulatory pathways to evaluate these tests, quickly & effectively
It is almost universal that any piece discussing Rapid Ag tests says “PCR is more accurate but…”
But even this isn’t true. It simply depends what you want to detect.
If wanting to identify ppl who are contagious, PCR is much less accurate.
If your goal is to detect ppl are infectious, a rapid Ag test is highly sensitive AND specific for this.
PCR is not specific for this. It will read positive even when not infectious. So… it’s less accurate for the public health question at hand “am I infectious”
You might say… well PCR is much more sensitive. But even that is not true. A bit more, yes, but if wanting to catch infectious ppl, it’s really but that much more sensitive and, if that’s your goal, then PCR is massively LESS effective than a rapid test.
A very important piece is the temporal relationship between when viral RNA is highest, when antigen tests are highest sensitivity and when people are most likely to be infectious following exposure. While almost no studies directly observe all three together...
@MarkZlochin@CircusPubes@DrPathHero1 They all fall directly in line with the exact same time period after exposure or - when symptoms are demonstrated, with the same period surrounding onset of symptoms.
So we really do not need empirical data showing transmission and viral load since the kinetics show it all
@MarkZlochin@CircusPubes@DrPathHero1 A major problem obtaining the direct empirical data is that if someone is testing, they likely aren't infecting others. So, people who are infecting others, you simply are not getting their swab at the same time as they are infecting. So relationships are skewed.
Luckily, the issue is a simple one to fix (all things considered).
The tests exist in HUGE numbers across the globe. Just not in the US. The reason? We've asked the FDA to take on an impossible task... to evaluate high quality PUBLIC HEALTH tools, when this is not their job
The FDA evaluates medical devices - and does not evaluate public health tools
This is THE problem. As long as we consider rapid tests as medical devices (they're not - they're PUBLIC HEALTH transmission detection tools) FDA is forced to fit a square peg in a round hole
While I am tremendously happy to hear the President say this.
I do have my reservations:
Time is of the essence. If we start the scaling process now, it will take a long time.
Meanwhile many many tests exist globally. We could be using those for the time being.
Importantly, I worry that the 280 million tests that are going to be purchased and produced with the use of the DPA... well, that's less than one test per person over the course of a year. The number sounds big but we do have 330 million ppl in US.
In 2015, along w Bryan Grenfell and colleagues, we discovered an exceptionally strong relationship between measles epidemics and all cause childhood mortality - following outbreaks of measles, child mortality was increased for 2-3 years.
We hypothesized then that measles was destroying B cells and plasma cells responsible for retaining immune memory. This is bc the measles virus specifically attacks immune memory cells via attachment to CD150 - a protein enriched on memory cells.
So on the positive side, if just getting a vaccine implies immunity per, then a positive response after a vaccine that is detectable by antibodies should imply that the person was vaccinated - thus protected.
But..on negative side - if someone fails to seroconvert to positive on EUA authorized Ab tests after vaccination... this would be crucial knowledge for someone to have and to talk to their doctor about.
FDA should be encouraging Ab testing post vaccine - esp serial measures
Just to be clear: 10% of the *detected* cases. Of course there were many more cases that no test picked up.
“If they had waited until they developed symptoms to get a PCR test, and then waited another 24 hours until they got the PCR results, that’s at least two days where they might have been unknowingly spreading the virus.”