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Comment by baybal2 | Hacker News Reader

That's an antibody test, not an RNA test. Quite a different thing.

It will only detect an infection when you have an immune response already. It will not if you don't.

RNA tests can detect the virus even if it doesn't turn a person diseased.

One reason people seem to be missing for why antibody tests are very useful is it will allow us to confirm those that are now immune. We can’t get this from the RNA testing because it’s primarily being used on only symptomatic people at the time they have symptoms (and then only if they can get the test which typically means severe symptoms)

But if we start to test widely for antibodies we can start to clear people from this effective quarantine/lock down situation we are going through. Those people can then start to go back to regular life (what’s left of it), moving around as normal, doing work helping others, so on, and that will help all of us (and of course the economy).

I don’t know if this is something that anyone official is talking about yet, but it seems like it should be.

> I don’t know if this is something that anyone official is talking about yet, but it seems like it should be.

I agree. I think this will greatly help with people's mental state, etc, plus they can help family and friends who are under quarantine. The question of how long immunity lasts, is it effective, etc is still a bit open. Also, how in a Western democracy do we distinguish (from the point of view of law enforcement personnel) between those who are immune and those who are breaking quarantine?

Perhaps requiring people to sew a red-colored letter to their clothing?

>are breaking quarantine

Happened today. Police can stopped outside our building Two policemen came out. One was holding a notepad+pen, and one was holding his cellphone. One was reading phone numbers and keeping notes, the other was dialing numbers, asking people to come out to their balconies so they see they are self-isolated and staying at their homes. Very simple and efficient way to see who stays and who runs.

Having antibody doesn't mean you can't spread the virus. For example, antibody tests are often used to diagnose HIV, but testing positive for HIV antibody (i.e. you are infected) doesn't mean that life will be normal.

That’s true. Though you could still buffer it with a “must be positive for N weeks” rule.

Also, while there would be concern about a positive but still shedding person coming into contact with one who hasn’t contracted it, there’d be no issue with them hanging out/working/etc with others who are positive.

Having antibodies and waiting 14 days to be safe will be good enough to be whitelisted.

Right now the only way to be whitelisted is having had a test done while being ill, but asymptomatic cases are unlikely to ever get tested.

> Those people can then start to go back to regular life (what’s left of it)

You sure that's not hyperbole? If you believe that, you need to turn off the news.

There is evidence that people can become re-infected, so antibodies aren't enough.

There’s not good evidence of that. There have been cases of people testing negative then positive again but that doesn’t mean they had cleared the virus and got reinfected. It more likely means they had a false negative. (E.g. I have a friend in hospital right now with COVID-19 that has had four tests, one positive, two negative, then one positive again, all tests within the space of four days.)

It also can be the case if you are immune compromised that you may clear the virus through good luck, drugs, and your innate immune response. But you never developed a good adaptive immune response and so don’t show a strong antibody response.

Immunity to this virus may not last 10+ years, but it’s seeming unlikely that is lasts less than 6 months.

> It also can be the case if you are immune compromised that you may clear the virus through good luck, drugs, and your innate immune response.

uh, how? Perhaps this is tangential, but it's important that anyone who is immunocompromised takes this seriously. Don't just think you'll be ok with a bit of luck. If you are immunocompromised your immune response is by definition weak and we have no working therapeutics.

Yeah, yeah, I know there are 2 promising ones but its not really clear. The Gilead one is fairly legit, but the protocol used to compare Chloroquine for covid is fucking bullshit. They compared people across hospitals, way too many things different, you can't actually draw any valid scientific conclusion - it's purely anecdotal (as thankfully Fauci made more clear to the public today).

I don’t think you read my comment in the context of what it was replying too. It was a response to someone saying people can get reinfected. The reports of this appears not to the case for the reasons I and others explained (false positives/negatives). I speculate it might possibly happen for real though in the case of immune compromised people who are lucky enough to survive, but due to being immune compromised do not mount a proper adaptive response. Thus develop no antibodies and and thus are able to be reinfected. Obviously that would be rare. (But so are these case reports that are driving these rumors of “reinfection” overall.)

Not really sure how you read that as somehow advocating immune compromised people do not need to take this seriously.

Wouldn't it then make sense to have camps where young, healthy adults can go to get immunity by intentionally getting infected and recover ? Then they can go back to having normal lives. The epidemiology version of a controlled burn.

If someone take the gamble of intentionally getting the virus, his/her life expectancy is reduced by 3 months (a ballpark figure).

If someone stay in isolation until a vaccine arrives, he/she may consider it a greater loss.

I am pretty sure some entertained this idea. The real problem is tail risk is huge. If a youth gets complications or dies from the virus - is the camp organizer responsible?

The problem is that with such a high rate of hospitalization or even death, even for young healthy adults, that’s a risky approach.

It might be necessary at some point, however.

Citation? IIRC all of the examples were either false positive re-tests or atypical patients (i.e. with some immune issue that only supressed the virus when they tested negative)

Citation?

I saw the one story about people "testing positive again" but that seemed to be a testing abnormality, not people getting sick a second time.

https://www.latimes.com/world-nation/story/2020-03-13/china-...

Time will tell, but from that article:

>Scientists in and outside China agree that reinfection is a highly unlikely explanation for the patients who retest positive. They say testing errors are more likely to blame — either false negatives that resulted in patients being discharged too early, or false positives when they retested and were taken back into hospital.

From my understanding, this should still detect the virus in individuals with mild or no symptoms, correct? Because those individuals do have an immune response.

But what you're saying is that RNA tests will have better recall during the initial stages of infection when the virus is multiplying in someone's body and that person doesn't yet have an immune response?

That I understand is totally correct.

It's important to test the public to see the penetration into the population. People who test positive should get an RNA test to determine if infected. People who are not infected become valuable assets to keep logistics and supply chain up and work front line tasks as they have little risk of getting infected. This group people can return back to normal life and don't need to be lockdown.

I can't help but ask... How much risk is "little risk" here? Can they still contribute to the spread? And what percentage of population can fall into this group?

We don't know.

The period of immunity following infections varies, and this virus is not well understood.

I think if you test positive with an antibody test but not an rna test it means your immune system has the ability to fight it off from a previous infection but the virus isn’t currently multiplying inside you.

If you're testing positive for antibodies and negative for the virus RNA itself it means your immune system has been exposed and recovered. This is also what you'd expect to see in someone that has been vaccinated. They would not be contagious at that point because the virus is not present. This is not the same as someone that gets infected but is asymptomatic - they would still test positive for RNA.

The percentage of the population that would naturally fall into this group would likely be very small given this is a novel virus so pretty much nobody's immune system had been exposed prior to a few months ago, and we're seeing pretty massive infection rates globally.

> That's an antibody test, not an RNA test.

Yes, this is an exposure test - which works okay for a completely novel virus like this one.

The real question is whether this has a drop-off factor for immunity for instance (i.e non-infectious herd immune) or if it can differentiate between exposure and carrier for the disease.

It might be useful right now, but it will get less useful as the months go by.

For instance, the QuantiFeron test for TB tests me as positive because my white blood cells take TB very seriously (or so it looks like).

Surely still important progress & a big deal though, right?

This will make it easier to tell if a symptomatic person has COVID or something else. But it won't help with early detection, which is what is most urgently needed.

We needed early detection weeks ago. That ship has sailed. At this point a test like this is probably more urgent. The lead time on getting tests for patients showing up to the hospital (i.e. they have symptoms) will make a massive difference in how much PPE the hospital goes through.

Early detection is utterly irrelevant at this point it’s endemic at most places now.

Exhaustive testing and selective isolation would be better than lockdowns, even if the virus is endemic. Testing is the bottleneck.

Testing is a bottleneck which is why you need as many testing venues as possible including mail-in at home tests for the more rural areas.

The US isn’t South Korea it’s population density is drastically different as well as its geographical scale which makes viral protein and RNA tests much harder to conduct.

At this point social distancing and a multi phase testing plan will be required which will undoubtedly include field AB testing to reduce the load on testing facilities.

AB testing also provides additional valuable data points including a more accurate infection figures since it can come out positive as long as the antibodies remain in your system.

Big chance of getting false-positive. People will think they're clear and won't distance themselves from vulnerable. While they may be carriers.

That would not be the effect of a false positive.

In any case, these tests would be used to confirm or rule out SARS-CoV-2 as the cause of someone's symptoms. They wouldn't be used for routine screening of asymptomatic people.

I don't know why you are being down voted. The risk is for false-negative, but you are right that people might think this is going to clear them.

Even the manufacturer/supplier warns that: "Negative results do not preclude SARS-CoV-2 infection and should not be used as the sole basis for patient management decisions. Negative results must be combined with clinical observations, patient history, and epidemiological information."

They also indicate: "The sensitivity is 97.90 %, the specificity is 91.77%."

But when you read the technical document you realize that this was for a subset of patient. The real numbers are 88.7% and 90.6% respectively, and again these are for severe cases.

I don't know how much precedent there is for this type of testing (have we used similar things for Ebola or SARS or measles or anything else?).

I've read that this will be useful in broad studies to track how widely the disease might have spread without being diagnosed. But will this type of antibody test eventually be available for any doctor to order for a patient? I'm just getting over a fairly mild but persistent chest cold which also had me with a slight fever last week, and would really like to know if it is/was covid-19 or not. Last week when I still had the worst of the symptoms, my doctor said I didn't meet enough of the criteria to be tested.

They are called serology tests and widely available for other viruses and bacteria. Its just that Covid-19 is such a new thing that the tests are just being developed.

I think it's likely useful for mild cases and for detecting people previously infected. People that recovered can be put to work in hazardous places. And can donate plasma to make serum[1] for treating sick people.

[1] Antivirals are a crap shoot but serum works hands down.

How about a source for that [1]

https://www.jci.org/articles/view/138003

It's far to early to call it a slam dunk for nCov-2, but it is a treatment already used for rabies and hepatitis.

One of my teachers in the 70's came down with HepA. Health department required all of us to get a immune globulin shot before returning to school.

It will also detect recent infection after the virus has been wiped out but the antibodies remain.

So this is much better than any RNA test to assess the progression of the disease through the population.

This also requires a blood sample, as opposed to a swab.

That's actually better, some competent people said, because the chance of contact with virus carrying bodily fluids is eliminated

Except people generally don't like needle sticks.

Trust me they like swabs less they are by far more uncomfortable than a prick.

Are you a doctor? If not, why are you commenting on things you have no expertise on?

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