Aroop Mohanty In the US, the government is talking using antibody to track who has already been infected by the virus, and issue a 'proof' pass to them, so they can go back to work and open the economy again.

Aroop Mohanty Also, according to a research results, certain antibody is not produced until after 10 days of onset of the disease. So, it is more accurate to test the antigen (virus itself) for COVID-19 patients.

agreeing with answer suggested by Yuan-Yeu Yau

Rapid antibody test is a supplementary tool to assess the prevalence of disease in the community; will be used only after 7 days of start of onset of symptom, important for epidemiological studies and surveillance purposes.

But the question here is that if the antibody test comes negative can the patient be labelled as covid negative and asked to return to normal work?

Aroop Mohanty The antibody test during lockdown is used to check if the results is 'positive' for someone. They are looking for people with 'positive' results, not 'negative' results. If you are positive, that means you already infected by the virus, and you have immunity (against the virus) to protect yourself. So, you can go back to work.

But the risky thing is that we don't know how long this immunity, if exist, will last. One month? 2 months? 3 months? or...longer??

See the link below:

https://nypost.com/2020/04/20/facui-urges-caution-about-relying-on-coronavirus-antibody-tests/

Quantitative antibody tests are required to reopen the economy. The quantitative test is not of clinical significance but of a policy nature as it can be used to determine exposure and immunity status of individuals. In an a symptomatic patient it is not necessarily indicative of an active case of the disease. Other tests remain more useful and cost effective for clinical treatment of the disease.

Aroop Mohanty

I think this is an important info regarding 'Antibody rapid test kit', which I posted for another RG question.

By far, there are already many 'antibody rapid test kits' flooding the US markets (other countries probably too). According to this report (see below), 70% of the kits tested were NOT consistent (results) [checked and evaluated in a scientific company]. Most of them are not approved by the US FDA (Food & Drug Administration); not go through the FDA scientific review. The FDA let companies to do self-validation. The FDA only approved 4 kits by far. So, next time if you want to buy an antibody rapid test kit for yourself, carefully check it out beforehand.

(This story was reported in the film below starting at 6:30)

https://www.youtube.com/watch?v=QwPLPK1ax3c

Published today. "COVID-19 antibody testing 'a disaster,' says Roche CEO, as diagnostics sales rise" (4/22/2020)

"Many countries are seeking serology (antibody) tests to better understand whether people are developing a possible immunity to the novel coronavirus. But reports detailing high rates of false-positive and false-negative results are delaying widespread screening. "

https://www.fiercebiotech.com/medtech/covid-19-antibody-testing-a-disaster-says-roche-ceo-as-its-diagnostics-sales-rise

Its also proven here in India where the antibody test kits have given us a big dilemna..some states have reported a total failure when they wanted to validate it...when used for 100 covid positive cases proved by RT PCR it only gave 5 of the 100 as positive..as a result of which they were withdrawn..

Is this true?

For antibody rapid test kit, Roche’s diagnostics chief Thomas Schinecker offered his view. “From a technological perspective, with a test using a finger prick, you will never get as good a result as if you take the blood from the vein.”

In Switzerland this test has been used to determine whether patients positive for COVID-19 did develop a natural immunity to the virus. Surprisingly only 5,5% of such patients did develop a specific antibody against the virus. This is obviously not enough to assure an auto immunization of a population while contracting the virus infection.

Jean-Pierre Jost The right word is "herd immunity". 'Auto immunization' can refer to a disease, where your immune system attacks your won body.**

**Medical Definition of autoimmunization: production by the body of an immune response against its own tissue constituents

https://www.merriam-webster.com/medical/autoimmunization

Serology tests are not recommended by WHO for identification of COVID-19 infection. It will be negative in window period.

Despite all the recommendations of the government, various centers in India have already started performing these rapid tests and that too without proper validation. These tests are only indicated for hotspot areas for surveillance and then if any patient is tested positive by these they have to be further confirmed by RT-PCR.

Validated SARS-CoV-2 specific antibody tests are useful for seroprevalence of COVID-19 in the population, for immunity of recovered patients after COVID-19 infection, and selecting people for go back to work and travel as "Immunity Passport"

However, WHO gives word of caution about immunity passports based on an antibody tests.

Further reading:

Cuomo: First Antibody Tests Show 21.2 Percent of City Residents Could Have Had Coronavirus

https://www.ny1.com/nyc/all-boroughs/news/2020/04/23/governor-cuomo-daily-coronavirus-update-with-first-antibody-test-results

"Immunity passports" in the context of COVID-19

https://www.who.int/news-room/commentaries/detail/immunity-passports-in-the-context-of-covid-19

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