Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Rapid Covid tests miss 90% of asymptomatic cases

nature.com

Post reply on HN
Print view View original

111–120 of 236 posts

Re: Rapid Covid tests miss 90% of asymptomatic cases

#111

Post by cmrdporcupine »

gjulianm wrote: post #109
cmrdporcupine wrote: post #81

Even symptomatic they've been pretty useless for our family. My daughter was sick with 'rona twice last year (the rest of us seem to have never gotten it) and in both cases it barely registered visually just once on the tests after doing many many tests that showed negative. So I wonder how many times they've shown us false negatives. My wife has suddenly just now become ill with something fever/fluish and it's testi…

> My daughter was sick with 'rona twice last year (the rest of us seem to have never gotten it) and in both cases it barely registered visually just once on the tests after doing many many tests that showed negative. Well, if anything your experience seems to confirm how these rapid tests work. At least my perception has always been that these were advertised to check not whether you had COVID or not (PCR is the gold…

Absolutely. The problem is that public policy in Canada was to get rid of more effective testing. PCR testing went away quite quickly, likely because it was very expensive. And so early on they deprived the public of the ability to diagnose and know whether they really had COVID before it was highly symptomatic (and spreading) but at the same left in place measures asking us to isolate etc.

The issue with COVID all along vs other respiratory viruses is that it had the potential to transmit before symptoms appear. Which made things like temperature checks, etc fairly useless at preventing its spread. So actually it was important to know in advance if you had it, at least before mass vaccination and omicron changed the profile of the way it spread it seems.

Schizophrenic public policy.

Also by last spring the only way to know what was happening with the virus' spread was to look at wastewater detection numbers.

Re: Rapid Covid tests miss 90% of asymptomatic cases

#112

Post by eightysixfour »

mike_hearn wrote: post #105
rlpb wrote: post #42

What I think really matters for most people is not to find out whether they have covid or not, but whether they are infectious or not. I'd really like to see research (any at all!) into how effective different test methods are at predicting infectiousness and am disappointed that this never seems to get addressed. Because who cares if you're asymptomatic but your viral load is low and you're unlikely to infect others…

It was researched and the results were beyond poor, which is why you never heard about them. IIRC ~75% of PCR positive samples couldn't have any virus cultured from them at all. Viral culturing isn't easy, but PCR tests can trigger on destroyed virus, so it's not a surprise that you can't get replicating virus out of many such samples especially at CT>40. But even if you can grow virus, that doesn't mean someone is i…

> People's immune systems differ significantly and some are just stronger than others.

Just a nit but stronger is a weird term to describe any functioning immune system. Some genetic trade-off that makes one immune system better suited to blocking COVID infection might make it worse at something else.

> To be infected I have to be infected but you have to be susceptible. The COVID models basically ignored this and assumed a homogenous population.

And the data used to drive those models is going to be a result of a real world average across the population, so that is fine for nation level decision making.

Let’s say you’re using data from two traced cases, a case with high susceptibility (HS) family members and one with low susceptibility (LS) family members.

The HS case was in contact with 4 family members, 3 of which became infected. The LS case was in contact with 4 family members and 1 became infected.

Two infections, 50% transmission rate. That is fine for modeling and policy, unless we have some sort of a test to determine if you are HS/LS which could be used to make more granular policies.

All of this is moot considering the the different variants we never reached some magical “herd immunity” anyways.

Re: Rapid Covid tests miss 90% of asymptomatic cases

#113

Post by blagie »

usednet wrote: post #63
blagie wrote: post #34

Earlier quoted context omitted.

.... maybe .... It depends on the purpose of the test. For example, a trillion dollar question is still long covid. Very significant numbers of people are on disability right now. About 10% of Americans have some form of long covid, and >1% are unable to work due to long covid (or >2% of the workforce). Long covid comes up even with mild and asymptomatic cases, and seems to have a strong autoimmune component. If you'…

I think its highly likely long COVID simply does not exist, at least in the way we currently imagine it. The body of evidence that long COVID has a biological/chemical/physical basis is very unconvincing. The demographics of the people who get long COVID is the most telling evidence that its more of a syndrome than an actual disease. Over 20% (!) of bisexual people have/had long COVID. Long COVID sufferers are more l…

Yeah, no. The science -- and basic common sense -- is against you. There are many people who are hypochondriacs and make stuff up. However, anecdotally, I know people who:

- Had severe memory problems for a few months following covid

- Had severe balance problems for a few months following covid (to the point of falling when walking around the house)

- Basically couldn't talk for a month after a mild covid infection, due to coughing fits (despite having mild/no respiratory symptoms during a very mild covid).

... and so on. These are not psychosomatic symptoms. You can't make up a hoarse voice with an extreme cough.

You can talk to doctors too. This stuff is pretty severe. If your argument was that, rather than 4 million people out on long covid disability, it was, say, 2 million, I'd listen. However, your argument is like someone near the equator arguing snow doesn't exist.

Under/over/misdiagnosis is a thing for a lot of conditions, but that doesn't mean those conditions don't exist.

You'd also be better off citing medical journals than conspiracy web pages with web surveys and sample biases.

Re: Rapid Covid tests miss 90% of asymptomatic cases

#114

Post by blagie »

zoklet-enjoyer wrote: post #60
jnovek wrote: post #48

Earlier quoted context omitted.

A cursory google suggests that post-viral fatigue from COVID is expected to last a few weeks. Long COVID can last months; I know at least one person who still has long COVID symptoms from an infection that occurred in April 2020.

Have they tried paxlovid?

I'd be very surprised if it helped. There's pretty good evidence that long covid isn't caused by persistent virus.

My own speculation is that it's autoimmune, simple due to having it seen resolved when people were vaccinated. However, "anecdote" is not the plural of "data," and it just as well be unrelated.

There are wonky changes to organs during covid, which many doctors speculate are the root cause.

In either case, I'm unaware of any mainstream theories where paxlovid would be likely to help.

Re: Rapid Covid tests miss 90% of asymptomatic cases

#115

Post by petre »

mike_hearn wrote: post #105
rlpb wrote: post #42

What I think really matters for most people is not to find out whether they have covid or not, but whether they are infectious or not. I'd really like to see research (any at all!) into how effective different test methods are at predicting infectiousness and am disappointed that this never seems to get addressed. Because who cares if you're asymptomatic but your viral load is low and you're unlikely to infect others…

It was researched and the results were beyond poor, which is why you never heard about them. IIRC ~75% of PCR positive samples couldn't have any virus cultured from them at all. Viral culturing isn't easy, but PCR tests can trigger on destroyed virus, so it's not a surprise that you can't get replicating virus out of many such samples especially at CT>40. But even if you can grow virus, that doesn't mean someone is i…

Also there was an outbreak at a Belgian Antarctic base. Incoming personel took PCR tests, tested negative and were also quarantined for 10 days in South Africa. Then they took an additional PCR test 48h before departure. Six days after arrival there was the first Covid case.

https://abcnews.go.com/Health/covid-outbreak-belgian-researc...

Of course, certain news outlets like for instance the BBC have failed to disclose these additional details.

Re: Rapid Covid tests miss 90% of asymptomatic cases

#116

Post by pc86 »

blagie wrote: post #38
pc86 wrote: post #35

Earlier quoted context omitted.

This doesn't answer the question. Why, if asymptomatic cases are unlikely to infect others, is a false negative for asymptomatic cases a problem? Doesn't this all boil down to "if you feel sick, stay home, if you don't, don't worry about it?"

unlikely ≠ won't Defense-in-depth gives a broad range of tactics, and the goal is to combine enough of them to limit risks.

"won't" isn't a reasonable standard. People get sick. You get other people sick. Other people will get you sick. It happens, and completely eliminating every occurrence is not a valid or reasonable goal.

Re: Rapid Covid tests miss 90% of asymptomatic cases

#117

Post by cortesoft »

harha wrote: post #85
gjulianm wrote: post #78

Earlier quoted context omitted.

Precisely the point of most of those policies was to use rapid tests to ensure you weren't being infections at that moment or close to it. I honestly don't know what's so controversial about them.

I can figure out for myself if I have symptoms or not

And you think everyone would disclose their symptoms?

Re: Rapid Covid tests miss 90% of asymptomatic cases

#118

Post by mike_hearn »

hospitalJail wrote: post #68
b0dhimind wrote: post #56

We are all "asymptomatic" with something. Asymptomatic people don't spread as easily anyways. Typical fearmongering tyranny propaganda to inculcate fear into society, simultaneously scaring unhealthy people and leading to policies to inhibit healthy people.

Not to mention, I think people are going to look back at something with a 1% death rate and wonder why we panicked so hard. Various winter viruses kill on the same order of magnitude, and they kill the same old, obese, sick population. I'm a bit worried we will have something awful, killing healthy people or large swaths 5-20% of the population, and we will be too desensitized to care. It def seems like it was a poli…

IFR was actually between 0.1% and 0.3% depending on what source you use. 1% was an early assumption back when there were only dozens of cases, but of course, back then only the most severe cases were being identified.

Re: Rapid Covid tests miss 90% of asymptomatic cases

#119

Post by spamizbad »

harha wrote: post #85
gjulianm wrote: post #78

Earlier quoted context omitted.

Precisely the point of most of those policies was to use rapid tests to ensure you weren't being infections at that moment or close to it. I honestly don't know what's so controversial about them.

I can figure out for myself if I have symptoms or not

How? I wouldn't know the difference between a seasonal cold (or flu) or COVID, mostly because I've never had COVID.

Re: Rapid Covid tests miss 90% of asymptomatic cases

#120

Post by gcanyon »

mike_hearn wrote: post #105
rlpb wrote: post #42

What I think really matters for most people is not to find out whether they have covid or not, but whether they are infectious or not. I'd really like to see research (any at all!) into how effective different test methods are at predicting infectiousness and am disappointed that this never seems to get addressed. Because who cares if you're asymptomatic but your viral load is low and you're unlikely to infect others…

It was researched and the results were beyond poor, which is why you never heard about them. IIRC ~75% of PCR positive samples couldn't have any virus cultured from them at all. Viral culturing isn't easy, but PCR tests can trigger on destroyed virus, so it's not a surprise that you can't get replicating virus out of many such samples especially at CT>40. But even if you can grow virus, that doesn't mean someone is i…

I've read several of your responses here, and thanks for the info, but I have to say, your tone comes off as "I know better and would have been more sensible if I were in charge."

When you're in the heart of an epidemic that's going to kill millions, you err on the side of caution. Quarantining you at home, for example, makes sense when you're dealing with a deadly disease and you don't know enough to know you're not contagious.

Again, thanks for the info, but "lessons learned" should generally be left to the people who will have to deal with the next pandemic, especially since (I'm betting) they won't express their lessons learned as confidently as you are.

Post reply on HN