
Roche CEO's says some Covid-19 antibody tests are a disaster - djsumdog
https://www.reuters.com/article/us-roche-results/a-disaster-roche-ceos-verdict-on-some-covid-19-antibody-tests-idUSKCN2240JS
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subaru_shoe
“Chief Executive Severin Schwan said on Wednesday as he prepares to launch the
drugmaker’s own antibody test next month.”

chevy calls fords new car garbage.

~~~
Renaud
But he still has a point.

Pushing all manners of unreliable tests will makes matters worse for everyone.

Any test will need a very high degree of reliability or you’ll end up with
large numbers of people being quarantined for nothing or, worse, large numbers
of people with the virus allowed to roam free as they believe they are not
carrying it.

~~~
Spartan-S63
The other issue is that we don't know what concentration of antibodies is
required for immunity. We know these things for other diseases, like
influenza, chickenpox, etc. We have no point of reference, so we can only test
for the presence of antibodies.

I think antibody tests are still likely to be useful, especially in collecting
data on the pervasiveness of the disease and getting information to find out
what threshold immunity occurs at. The messaging around them is rife for
misuse, though.

Everyone is looking for a silver bullet, but all we can do right now is the
long, slog of science to get to a place where it's truly safe to try to return
to a semblance of normalcy.

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gumby
I agree, the people who want “the red tape eliminated — lives are at stake”
are nuts. Garbage data is garbage data and getting it sooner doesn’t help.

False negatives can cause someone contagious or sick to go out and infect
others; false positives can cause unnecessary treatment and take up hospital
resources that should have been spent on actual patients.

~~~
viggity
From what I gather a false positive for an antigen rtPCR is essentially
impossible. The primers are extremely specific and can't find something that
isn't there.

A false positive for an antibody test is unlikely to take up hospital
resources. They admit people to the hospital for symptoms like
dyspnea/hypoxia. Not because the patient tested positive on either the
antibody or antigen test. The danger in a false positive for an antibody test
IgG or IgM, means gives the patient a false sense of security that they've
already gotten the virus and are thus immune in the short to medium future.

~~~
logicallee
>a false positive for an antigen rtPCR is essentially impossiblee. The primers
are extremely specific and can't find something that isn't there.

I read somewhere that among the reasons for a false positive would be cross-
contamination among samples.

Just because the primers find something in the sample, doesn't mean that that
something isn't in fact merely a bit of cross-contamination from another, true
positive, sample.

~~~
xscott
I was watching this video earlier tonight:

[https://youtu.be/Vat-PKdQ13A?t=30](https://youtu.be/Vat-PKdQ13A?t=30)

That looked like some really sloppy lab technique, and I hope that's not how
it is really done in practice. If real tests are done by hand like this, with
distractions, open air, and no mask on the technicians, it's easy to imagine
false positives.

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mynegation
So how statistically independent is the error between serological tests? If we
make 5 tests on the same blood sample and go with 3 or more out of 5 rule,
would that help with FP and TP?

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jxramos
Proportionality frequently seems to escape journalists, why be satisfied with
reports being confined to the qualitative and non-quantified realm? Give us
some background please. In this molecular diagnostics domain what are typical
figures for sensitivity and specificity? FDA lays down requirements for such
things right? Anyone know off-hand what percentages are required for a
diagnostic testing product to be released? For these tests in question how far
off from those marks are we exactly?

~~~
DenisM
There is no "typical" I'm afraid. Whether a test is useful or not depends on
error rates, priors, and application of the result.

For example, consider this scenario:

\- Virus has R0 of 2.5

\- the test for the current infection (i.e. not antibody) is cheap and
abundant

\- the test has 20% false positives

\- the test has 20% false negatives

\- Application: test every single person and confine everyone who tested
positive to their homes, releasing the rest. Repeat weekly. Take no other
action.

Result #1: 20% of the population are in isolation. 20% of your economy is
stalled, rather than 100%.

Result #2: 1 in 5 infected will go undetected. Still 4 out of 5 are isolated,
reducing the number of infected out there by a factor of 5, therefore your R0
drops from 2.5 to 0.5 The number of infected people on the street gets cut in
half every week. Epidemic fizzles out.

So even low-precision tests are useful. What is useless is tests that do not
have a reliable metric for false positive / negative. Which is what many of
the AB tests are.

~~~
perl4ever
"Result #1: 20% of the population are in isolation. 20% of your economy is
stalled, rather than 100%."

This bugs me, because in this hypothetical, you're implying something as a
point of comparison which is nothing like reality. 100% of the population is
_not_ in isolation - the only people who are in isolation are those who have
had such severe symptoms they've been tested and it came back positive, or
they're really obviously linked to such a person. And obviously 100% of the
economy is not stalled; it may not be precisely clear what the impact is so
far, but people are talking about _single digit_ GDP percentage point
declines. If you frame that as the worst economic news since the great
recession, or put it in context with the job losses, it's pretty bad, but it
clearly could be ten times worse and it's not.

I get that maybe you meant it as just an example and specifics aren't
important to your point about statistics, but I feel like I've read similar
posts to yours that kind of get the nonsensical scenario out there, that we've
shut down "100%" to where people kind of get used to it even though it's not
reality.

~~~
Retric
US’s isolation started very late in Q1. It requires a very large decline to
average out to ‘just’ 1%.

~~~
perl4ever
I don't feel that makes a difference to what I just wrote. But I can do some
very rough arithmetic along those lines to see what the decline would have to
be.

The GDP figure just reported is -4.8%. Based on what I recall, the inflection
point was about halfway through March. Friday the 13th is when the state
government in NY finally said anyone who can, work from home. That's 0.5/3
months or ~17% of the quarter I'd assign to "shutdown".

0.83 * 1 + .17 * x = .952

...I don't trust myself to do high school algebra, so I asked Wolfram Alpha
and it said x = 72%. Ok, so the reported figure of nearly -5% probably equates
to a little over a quarter of the economy missing.

I don't think I need to concede my point about a 100% stoppage not happening.

~~~
Retric
The larger point stands it’s just ‘but people are talking about single digit
GDP percentage point declines‘ that I was correcting. That said, Pennsylvania
and several other states waited until April to order a shutdown, but the
observed GDP decline was annualizing a ~1% though there was growth in the
ready of Q1.

Long story short, that 4.8% is absolutely worthless.

~~~
perl4ever
The bit you quote from me seems strictly accurate; by single digit I mean <
10%. That is what the news is reporting. It is factual, and my inference that
the economy is not shut down hasn't been questioned.

Saying that the difference is larger when you consider only part of the
quarter is correct too, but 4.8% is not "absolutely worthless", it just needs
to be interpreted properly.

As in my previous comment, you can approximately derive the actual amount of
decline, which is a fraction of a complete shutdown.

~~~
Retric
By absolutely worthless I mean it’s a meaningless calculation. They take the
actual change averaged out over a quarter, and then assume 4 more quarters
will have exactly the same thing happen.

It’s a common calculation used to make quarterly numbers seem more important,
but it’s at best misleading if not actively deceptive.

~~~
perl4ever
Wait, wait, wait. Nothing is "meaningless" if it contains information. And
"misleading" depends entirely on context.

It sounds as though you are suggesting I made an error that _increases_ the
apparent size of the shutdown, meaning it is actually _smaller_ and my claim
is _stronger_ than I thought.

If the figures are annualized (I checked* and I think you're right) then it
improves my original point - the 4.8% decline becomes 1.2% un-annualized, and
the normal trend of +2% becomes +0.5%.

The equation should then be something like .167 * x + .833 * 1.005 = .988, "x"
being the percentage of the economy active in the last half month, or about
90%.

I'm confident that there is information in the reported figure and that no
reasonable calculation can show the economy was shut down completely.

*[https://www.bea.gov/data/gdp/gross-domestic-product](https://www.bea.gov/data/gdp/gross-domestic-product)

~~~
Retric
You’re ignoring information that you disagree with. Yep, of the multiple
errors in your calculation, one of them lowers the estimate. But, I never said
anything about a 100% shutdown just that single digit comment.

Going in the other direction, picking the earliest possible starting date
underestimates the impact as does ignoring panic buying. Layoffs where also
not instantaneous, and people’s final paychecks are delayed etc. All of this
is going to show up in Q2 numbers even if many states are scaling back their
shutdowns.

As to being a meaningless calculation, you’re describing a reversible
calculation not a useful one. I can type a message in ROT13 and the result
contains the same content, that does not make me doing the ROT13 useful.

~~~
perl4ever
"You’re ignoring information that you disagree with"

You're the one saying information is "meaningless", and at the same time I
don't see any alternative data that you've provided. You're just making
general statements that sound to me like the fallacy that imprecision means no
information.

In your first reponse to me, you wrote: "It requires a very large decline to
average out to ‘just’ 1%"

So, "very large" is subjective, but I don't think 10% is "very large" _in the
context of people talking about 100% of the economy being down_.

~~~
Retric
> imprecision means no information

It’s imprecise enough that you’re better using other means to estimate the
decline. I am between 1cm and 1 mile tall, is true but does not convey new
information.

Similarly without knowing how fast was the economy was growing or shrinking
before the decline, the decline hit, when peak decline hit, it’s impossible to
say how bad things where at the end of the quarter beyond well it’s worse. I
mean presumably when news of the outbreak hit but before the shutdown there
was some effect, but I don’t know if it was a net positive or negative.

If you want numbers I would say 10+x larger is objectively a very large
decline relative to 1%. Anyone talking about a 100% shutdown while still
buying food is being using hyperbolic or simply does not understand what their
words mean. It’s at best symbolically true in that net wealth is being
destroyed so the engine of human progress has shut down.

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joezydeco
So do we have any data showing that the presence of antibodies equals
immunity? What exactly is the test telling us as of today?

~~~
williamstein
Antibody tests also help estimate how many people have been exposed to sar-
cov-2, which helps in making more accurate epidemiological models...

