Coronavirus Antibody Testing Finally Available, But Is It Reliable?

We finally have access to SARS-CoV2 antibody testing in the US, as of just a few days ago. But will this information help us better understand what we’re dealing with?

According to recently published (not yet peer-reviewed) Chinese data, levels of antibodies to SARS-CoV-2 vary widely in patients after recovery from novel coronavirus disease (COVID-19) — and in some patients, antibodies are undetectable.

There were only 175 patients who had recovered from COVID-19. All patients had been hospitalized with confirmed “mild,” infection. Antibodies were measured in plasma collected at the time of discharge.

Overall, 30% of patients had very low levels of SARS-CoV-2-specific antibodies, and of these, 10 patients (6% overall) had undetectable antibody titers. Those with undetectable titers at discharge still had undetectable levels two weeks later.

https://www.medrxiv.org/content/10.1101/2020.03.30.20047365v1.full.pdf

For our lay-readers, the body usually requires 2 to 3 weeks to mount an effective antibody response, so this data appears to have given the body sufficient time to make antibodies.

Six patients had antibody titers measured at different points in their disease course. Titers peaked at roughly 10–15 days after illness onset and remained stable thereafter.

The researchers conclude, “These results revealed that a proportion of patients infected with SARS-CoV-2 would recover without developing high titers of virus-specific [neutralizing antibodies]. How these patients recovered without the help of [antibodies] and whether they were at risk of re-infection of SARS-CoV-2 should be further explored.”

Infectious disease specialist Dr. Paul Sax explained that “Studies of serologic response after COVID-19 are in their infancy, and we should expect larger more representative analyses as antibody testing rapidly becomes more available. What’s even less clear is how these responses (or lack of them) correlate with susceptibility to re-infection.”

In Summary:

There will be data tens of thousands of antibody tests published throughout the world in the coming weeks, which will be much more reliable than what we can determine from 175 patients. If it turns out to be true that many people do not mount a measurably effective antibody response, this could turn-out to be useful information for scientists working hard on vaccines. If a vaccine could potentially provoke a more effective antibody response than the actual viral infection itself, then we can potentially immunize people in any stage of the illness and derive benefit. This includes those who have already recovered from Covid-19 but have insufficient or no measurable antibodies. This could actually be an exciting discovery!

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Justin Groode MD | Patient Advocate Alliance LLC

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