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

New Abbott SARS-CoV-2 antibody test has 99.90% specificity and 100% sensitivity

jcm.asm.org

Post reply on HN
Print view View original

261–270 of 275 posts

Re: New Abbott SARS-CoV-2 antibody test has 99.90% specificity and 100% sensitivity

#261

Post by apatters »

IanCal wrote: post #252
apatters wrote: post #234

Earlier quoted context omitted.

What specific evidence would you be expecting to see in December or January? The infection fatality rate for this disease is probably below 1%, and we don't know what percentage of the population is infected. We don't truly know how quickly it spreads. Nursing home populations are at greater risk, but even if the IFR is 3-5% for that cohort, the population mortality would be some fraction of that, and most of the dea…

> Nursing home populations are at greater risk, but even if the IFR is 3-5% for that cohort, the population mortality would be some fraction of that, Looking much higher than that. 80+ is 15-20% and 70-79 is 8% ( https://www.worldometers.info/coronavirus/coronavirus-age-se... ). It'll be concentrated more in people with pre-existing conditions so I expect nursing homes would see greater figures than that. > Statistic…

> Looking much higher than that. 80+ is 15-20% and 70-79 is 8%

The percentages you're citing are from the Chinese CDC [1] and represent the case fatality rate. They don't represent the infection fatality rate, let alone the overall population mortality. There's a big difference between these numbers which has been repeatedly ignored in the popular media, they keep on taking the scariest one (CFR) and presenting it in an unbalanced context. [2]

(To be fair, CFRs are the numbers we are the most certain about, but when you cherrypick the worst ones like the newspapers do they're also the scariest and least useful.)

The working definition of CFR in the Chinese study is basically people who saw a doctor, were suspected or confirmed of having COVID, and then died. But many other people would have caught the disease and not been seen by a doctor. Most of them would have been milder cases and they wouldn't have died. Key point is this number is not at all indicative of total Covid-related mortality in an exposed population.

The Kirkland story is really tragic, but it's just one data point and doesn't prove that ~15% of all nursing home populations will die. The conditions in other nursing homes could be very different, in fact that nursing home in Kirkland has since been investigated and fined $600,000 for unsafe practices [3].

[1] http://weekly.chinacdc.cn/en/article/id/e53946e2-c6c4-41e9-9...

[2] https://en.wikipedia.org/wiki/Case_fatality_rate

[3] https://komonews.com/news/coronavirus/kirkland-nursing-home-...

Re: New Abbott SARS-CoV-2 antibody test has 99.90% specificity and 100% sensitivity

#262

Post by taeric »

raducu wrote: post #247
taeric wrote: post #208

Earlier quoted context omitted.

Don't forget to factor this breaking through to long term care facilities. From the last I looked at this, if it had not hit long term care, the number of deaths would have been low enough that it may have gone undetected longer. (In WA, 92% of the deaths are still folks over sixty! I don't know the numbers for how many of them were in long term care.) Which is to say, you can't just look at the population death rate…

A friend of a friend got released from the hospital, she had covid-19 and was searching for an oxygen concentrator for her (permanent?) lung damage. She's 29 and otherwise healthy. I'm sure we would have noticed this disease without the high mortality rate among the elderly.

I'm sure we would have noticed. I'm not sure we would have noticed as quickly. We certainly would not have tested to find that nearly a quarter of NYC could have it.

Yes, it can do damage and is very dangerous for an at risk group. No, we don't know who that is, yet. Age clearly proxies for a risk factor. But which one?

Unless you are wanting to claim that no children have gotten this. Which, seems highly unlikely. (Or is the risk whether it will provoke an immune response?)

Re: New Abbott SARS-CoV-2 antibody test has 99.90% specificity and 100% sensitivity

#263

Post by taeric »

postingawayonhn wrote: post #238
taeric wrote: post #208

Earlier quoted context omitted.

Don't forget to factor this breaking through to long term care facilities. From the last I looked at this, if it had not hit long term care, the number of deaths would have been low enough that it may have gone undetected longer. (In WA, 92% of the deaths are still folks over sixty! I don't know the numbers for how many of them were in long term care.) Which is to say, you can't just look at the population death rate…

> Don't forget to factor this breaking through to long term care facilities. If they're not taking any precautions (because there's no knowledge of the virus in the community) then it can spread to those types of facilities very easily. In New Zealand where only 1,500 people have have COVID-19 (likely to be very accurate, 200,000 tests have been conducted) there's already been two outbreaks in nursing homes.

Certainly. I am not implying that we should just let it run its course. Just as I would not let any disease we have a vaccine for loose in a nursing home without the vaccine.

I just think the total IFR actually undersells how dangerous this is.

Re: New Abbott SARS-CoV-2 antibody test has 99.90% specificity and 100% sensitivity

#264

Post by guscost »

risaacs99 wrote: post #119
elorant wrote: post #110

Earlier quoted context omitted.

Viruses tend to become less lethal as time passes, not more.

I keep reading people asserting this, and I assume it's because we believe that a virus that becomes less lethal would have an evolutionary advantage. But, wouldn't lengthening the incubation period also be a successful evolutionary strategy regardless of lethality? It seems to me that there are many possible strategies that a mutating virus might gain an advantage and we shouldn't just assume that the only one that…

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4873896/

> Trade-offs between different components of parasite fitness provide the dominant conceptual framework for understanding the adaptive evolution of virulence (Alizon et al. 2009).

...

> By far, the most widely studied trade-off involves transmission and virulence (Anderson and May, 1982; Frank, 1996; Alizon et al. 2009). Transmission and virulence are linked by within-host replication: increasing parasite abundance increases the likelihood of transmission, but also increases the likelihood of host death; mathematically, this assumption can be formalized by making transmission rate β an increasing function of parasite-induced mortality rate ν. Nearly all of the literature we summarize below assumes this trade-off. However, another potential trade-off suggested by an examination of R0 involves virulence and recovery rate (Anderson and May, 1982; Frank, 1996). This trade-off is also mediated by replication rate, with high abundance increasing the likelihood of host death, but also decreasing the likelihood of the host clearing the infection (Antia et al. 1994); mathematically, this assumption makes recovery rate γ a decreasing function of parasite-induced mortality rate ν.

Re: New Abbott SARS-CoV-2 antibody test has 99.90% specificity and 100% sensitivity

#265

Post by CydeWeys »

Marsymars wrote: post #192
CydeWeys wrote: post #137

Earlier quoted context omitted.

Similar story here, had COVID-19-like symptoms in mid-March, but the Abbott test (administered at CityMD) came back negative. It makes me wonder what exactly is going on with this test. Do some people not produce antibodies? Is it overly specific to one strain of the virus and other people in NYC got a different strain that doesn't produce compatible antibodies? Was there some non-COVID-19 respiratory infection that…

> Was there some non-COVID-19 respiratory infection that hit NYC at around that same time that went under the radar? Not really under the radar, there are always a lot of respiratory illnesses. In my area, after reducing non-covid cold/flu by an order of magnitude due to social distancing, we're testing everyone with cold/flu symptoms, and they're still ~96.5% not covid-19.

Yeah, but I'm in NYC. Since some inflection point in March the vast majority of patients presenting with these symptoms do in fact have COVID-19. Being the global epicenter of the pandemic will do that :/

Re: New Abbott SARS-CoV-2 antibody test has 99.90% specificity and 100% sensitivity

#266

Post by CydeWeys »

aklein wrote: post #203
CydeWeys wrote: post #136

Earlier quoted context omitted.

Here's my opposite anecdote: I live in NYC and in mid-March I had all of the headline COVID-19 symptoms, including most notably shortness of breath (which I've never before experienced in my life short of high altitude hiking). I got the Abbott test two weeks ago, and the result came back negative. I was so sure I'd had it, but now it's looking like maybe I didn't.

I remember reading that some people, especially those under 40, don’t develop observable antibodies. Or, could’ve just been the flu. https://www.nytimes.com/2020/05/07/health/coronavirus-antibo...

"Because tests to diagnose coronavirus infection were unavailable to most people in New York City in March, the researchers included another 719 people in their study who suspected they had Covid-19 based on symptoms and exposure to the virus, but in whom the illness had not been diagnosed.

In this group, the researchers found a different picture altogether. The majority of these people — 62 percent — did not seem to have antibodies.

Some of them may have been tested too soon after their illness for antibodies to be detectable. But many probably mistook influenza, another viral infection or even allergies for Covid-19, Dr. Wajnberg said."

Yeouch, that could be me in that group. Also:

"The team tested 624 people who had tested positive for the virus and had recovered. At first, just 511 of them had high antibody levels; 42 had low levels; and 71 had none. When 64 of the subjects with weak or no levels were retested more than a week later, however, all but three had at least some antibodies."

It's been well past the 3 weeks for me that they're recommending. I'm gonna get another test and if that also comes back negative, it seems likely that I didn't actually have it.

Re: New Abbott SARS-CoV-2 antibody test has 99.90% specificity and 100% sensitivity

#267

Post by Marsymars »

CydeWeys wrote: post #265
Marsymars wrote: post #192

Earlier quoted context omitted.

> Was there some non-COVID-19 respiratory infection that hit NYC at around that same time that went under the radar? Not really under the radar, there are always a lot of respiratory illnesses. In my area, after reducing non-covid cold/flu by an order of magnitude due to social distancing, we're testing everyone with cold/flu symptoms, and they're still ~96.5% not covid-19.

Yeah, but I'm in NYC. Since some inflection point in March the vast majority of patients presenting with these symptoms do in fact have COVID-19. Being the global epicenter of the pandemic will do that :/

Slim majority, not vast - NYC test positivity rate peaked at around 55% IIRC.

Re: New Abbott SARS-CoV-2 antibody test has 99.90% specificity and 100% sensitivity

#268

Post by CydeWeys »

Marsymars wrote: post #267
CydeWeys wrote: post #265

Earlier quoted context omitted.

Yeah, but I'm in NYC. Since some inflection point in March the vast majority of patients presenting with these symptoms do in fact have COVID-19. Being the global epicenter of the pandemic will do that :/

Slim majority, not vast - NYC test positivity rate peaked at around 55% IIRC.

A lot of those tests were people not presenting with COVID-19 symptoms though. Think of all the asymptomatic people who were getting tested; that group had a much lower test positivity rate than 55%, thus bringing the average down. For people who had all the right symptoms, it was higher than 55%.

Re: New Abbott SARS-CoV-2 antibody test has 99.90% specificity and 100% sensitivity

#269

Post by Marsymars »

CydeWeys wrote: post #268
Marsymars wrote: post #267

Earlier quoted context omitted.

Slim majority, not vast - NYC test positivity rate peaked at around 55% IIRC.

A lot of those tests were people not presenting with COVID-19 symptoms though. Think of all the asymptomatic people who were getting tested; that group had a much lower test positivity rate than 55%, thus bringing the average down. For people who had all the right symptoms, it was higher than 55%.

That effect doesn't seem like it would skew a larger difference between Alberta and NYC test positivity rates. If anything, that would depress Alberta test positivity rates more than NYC ones, since we've got more spare testing capacity for people without all the right symptoms.

Re: New Abbott SARS-CoV-2 antibody test has 99.90% specificity and 100% sensitivity

#270

Post by CydeWeys »

Marsymars wrote: post #269
CydeWeys wrote: post #268

Earlier quoted context omitted.

A lot of those tests were people not presenting with COVID-19 symptoms though. Think of all the asymptomatic people who were getting tested; that group had a much lower test positivity rate than 55%, thus bringing the average down. For people who had all the right symptoms, it was higher than 55%.

That effect doesn't seem like it would skew a larger difference between Alberta and NYC test positivity rates. If anything, that would depress Alberta test positivity rates more than NYC ones, since we've got more spare testing capacity for people without all the right symptoms.

What does Alberta have to do with anything?
Post reply on HN