In August I wrote a story questioning whether PCR tests are too sensitive. Many clinical microbiologists and others took issue with the piece because they saw it as undermining the PCR. This Medium post raises some of those points: 1/x…
The post makes some very important points about PCR, including the huge variability across machines of cycle thresholds (Ct) and even from sampling method. 2/x
The FDA's own analysis confirms this concern. See, for eg, this recent attempt at figuring out the analytical sensitivity of some of the tests with an EUA, the range is very wide: 3/x…
So I can see why these scientists would not want to see an adoption of a universal Ct cutoff. But there is already a threshold for tests to spit out a pos/neg. The article was saying, what if we actually reported those, and looked at trends? 4/x
This too is controversial, I know, because of the variability, but several papers have shown a trend between Ct values and severity. Wouldn't it be worthwhile to records Cts (for each machine) and try to understand what the trends are for that machine? 5/x
The criticisms of my article aside as "simple," which I of course don't agree with, there is clearly a debate here, and not one in which either side should declare victory and walk away feeling righteous. 6/x
On one side are PCR supporters, who rightly feel that we need the most sensitive test for each individual's diagnosis. But OTOH, we have massive delays in getting answers and rising caseloads, so what good is a great test if it's not available to everyone or in time? 7/x
We obviously need other solutions, and I'm not sure dismissing any conversation about one as simplistic or misguided serves anyone. What is the solution to the logjam issue? 8/x
And by the way, I don't believe in the "don't talk about it because it will become twisted by people with an agenda" camp. Show me any issue in this pandemic, even one as straightforward and benign as wearing cloth masks, that hasn't become twisted? 9/x
That is not an argument for not openly raising issues with an existing test. There are some scientists who have talked about it openly, but many more believe that we should be recording and reporting Ct values than it seems like from Twittter 10/x
If you don't start from the point of condescension and dismissiveness, surely there are important issues here to be discussed and debated? 11/x
and btw, I'm not a scientist with a viewpoint, I'm just here to report on these issues as they arise, a distinction that I think sometimes gets missed. And I'm interested to see where this one goes, too. 12/12

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More from @apoorva_nyc

19 Oct
NEW: The Great Barrington Declaration has received a lot of attention, especially from the Trump administration. How did they gain access? And what exactly do they envision? 1/x…
Here are some of the main pts: 1) protect the older/vulnerable while letting young people get infected
2) No testing of asymptomatic people
3) No contact tracing. 2/x
BUT how exactly would this work? How do you define, let alone "protect the vulnerable," when a third of the population has underlying risk factors? And how do you physically separate them from the rest of the population? 3/x
Read 6 tweets
16 Oct
There are SO MANY concerns about rapid tests for the coronavirus but a real-world experiment in SF has found that Abbott's BinaxNOW is just as good as PCR at detecting people who are infectious…
The study is small, and it has limitations. But the team tested people at a train station in a Latino neighborhood. Looking at a likely range for infectiousness (CT < 33), the test detected 15 of 16 cases picked up by PCR. 2/x
But not rapid tests are equal. and neither, by the way, are all PCR tests. One analysis by the FDA found massive differences in sensitivity, with another Abbott test, ID now, towards the bottom. 3/x
Read 6 tweets
14 Oct
NEW: President Trump has been saying his immunity makes him feel like Superman. But the treatments he got may have prevented his body from making antibodies of his own, leaving him more susceptible in a few weeks than the average Covid-19 survivor. 1/x…
The Regeneron antibodies have a half life of 21 and 25 days. meaning that by Oct 23, their levels in his body will fall by half and then keep declining. 2/x
Mr. Trump did not have antibodies of his own when he got the Regeneron cocktail. The cocktail suppresses virus + dexamethasone tamps down immune system, so there's a good chance he didn't make any antibodies. 3/x
Read 5 tweets
13 Oct
NEW: Reports of reinfection with the coronavirus, like the one in Nevada, evoke a nightmarish future: Repeat bouts of illness, impotent vaccines, unrelenting lockdowns — a pandemic without an end. But that nightmare doesn't reflect reality. Here's why 1/x…
What these cases tell us is that reinfection is possible, and in at least 3 cases so far, have been more severe. But that’s well within the natural variation in immune response and happens with every pathogen. 2/x
Take a look at the numbers: > 38 mil reinfections; fewer than 5 confirmed with peer review. “That’s tiny — it’s like a microliter-sized drop in the bucket” said @angie_rasmussen 3/x
Read 6 tweets
12 Oct
NEW: Everyone is talking about the Regeneron and Lilly monoclonal antibodies. But some scientists are betting on "Prometheus," a ragtag group of scientists who are months behind in the competition — and yet may deliver the most powerful antibody. 1/x…
The Prometheus antibody won’t enter human trials till December, but unlike other mabs which would last weeks, the Prometheus would last up to 6 months. 2/x
It is also one of the only mabs that broadly neutralizes the new coronavirus, SARS and also other bat-origin coronaviruses. Meaning it’s a good weapon in the arsenal for any future coronaviruses that might decide to drop by. 3/x
Read 6 tweets
8 Oct
BREAKING: It's not just the monoclonal antibodies the Prez took: Remdesevir, and many coronavirus vaccines also rely on cells derived from fetal tissue -- exactly the kind of research the administration has curtailed 1/x…
And yes, I do know that the policy excludes the fetal tissue derived before June 2019. But it's exactly the kind of research that would not be possible under the ban today. 2/x
Even if the ban applied to these cells, Regeneron, Lilly and Gilead would be exempt because they are not funded by the government. Same would not be true of the vaccine companies which do get federal funds. 3/x
Read 6 tweets

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