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What Do COVID-19 Antibody Tests Show — and Can the Results Be Trusted?

Doctor Michael Saag has already had COVID-19, and a latest blood check confirmed his antibodies in opposition to the SARS-CoV-2 virus are by way of the roof. However the infectious illness specialist isn’t taking any possibilities, and nonetheless wears full private protecting gear when seeing COVID-19 sufferers.

“I don’t wish to be cavalier and expose myself to individuals with identified an infection and get contaminated once more. That may be sort of silly,” says Saag, a professor of medication and infectious ailments and director of the Middle for AIDS Analysis on the College of Alabama at Birmingham.  

As all 50 states reopen to a point, enormous questions stay about how widespread the novel coronavirus actually is throughout the nation, whether or not reopening could be performed safely at this level, and whether or not individuals who have already had the virus are protected in opposition to re-exposure. Discovering solutions hinges largely on testing for antibodies in individuals’s blood.

Whereas a whole lot of such exams have flooded the market in latest weeks, consultants say we don’t know sufficient about SARS-CoV-2 antibodies or the exams themselves to know what the outcomes actually imply.

The Worth of Antibody Testing

Antibodies are Y-shaped proteins that the physique produces to battle off an an infection. There are a number of varieties of antibodies, together with immunoglobulin M (IgM) antibodies, which have a tendency to point out up early to a battle in opposition to an infectious agent, and IgG antibodies, more refined fighters that arrive a number of weeks after an infection. The presence of those antibodies within the blood signifies somebody has been contaminated with a illness like COVID-19 previously, and the physique has fought it off.

On condition that a large percentage of infected individuals solely develop gentle signs or no signs in any respect, widespread antibody testing might give us a a lot better thought of how many individuals have already had the illness. This data may help inform coverage and provides epidemiologists a greater thought of what proportion of individuals contaminated with COVID-19 are dying. It might additionally assist us determine people whose antibodies might probably be used to deal with severely in poor health sufferers. 

However we don’t but know if having the antibodies means you might be protected in opposition to extra publicity to the virus. “Even in my scenario, I’m not assured that I can’t be reinfected and couldn’t get sick once more, we simply don’t know that,” Saag says.

Preliminary analysis on COVID-19 antibodies affords small indicators of hope on this level. A small examine printed within the Proceedings of the Nationwide Academy of Sciences in late April found plasma from patients who fought off COVID-19 improved outcomes for 10 severely in poor health adults. Two research printed this week in Science discovered monkeys infected with or vaccinated against SARS-CoV-2 had protecting immunity from subsequent infections. Further analysis printed in Nature this week discovered antibodies from a person who recovered in 2003 from SARS-CoV — a coronavirus strain that sparked an earlier outbreak — neutralized the SARS-CoV-2 virus within the lab. 

All this assumes the exams are dependable and correct — and, proper now, that’s an unknown.   

What We (Don’t) Know About Assessments

To present an correct end result, antibody exams have to be both sensitive and specific. A delicate check will present a small variety of false adverse outcomes; a selected check will give few false positives. Usually, these sorts of exams are validated by testing a whole lot, if not hundreds, of individuals earlier than incomes approval from the FDA.

In late February, nonetheless, the FDA announced that SARS-CoV-2 blood exams may very well be offered with out FDA approval in the intervening time, if the check maker notified the company and evaluated the check for accuracy. The objective was to advertise the fast creation of and entry to an important testing device. Dozens of antibody exams shortly flooded the market. Whereas the company has evaluated and granted a handful of exams with emergency use authorizations, many extra stay untested.

Efficiency varies vastly from check to check, says Patrick Hsu, assistant professor within the division of bioengineering on the College of California, Berkeley, and one of many leaders of the COVID-19 Testing Project, which has evaluated at the least 10 of those exams now in the marketplace. The FDA not too long ago acknowledged this drawback in an update to its March decision, writing that “a regarding variety of business serology exams are being promoted inappropriately, together with for diagnostic use, or are performing poorly based mostly on an unbiased analysis by the (Nationwide Institutes of Well being).”

“What we’ve acquired now could be chaos,” says Saag. Suppliers need to do their very own homework on the sort of check they’re utilizing, the check’s traits and efficiency, and nonetheless take the outcomes with a hefty grain of salt. “I’ve been advising many of the sufferers to postpone getting an antibody check till the mud settles a bit.”

This week, the FDA started cracking down on unproven antibody exams. The company printed a list of 28 test manufacturers which have both already withdrawn their exams from the market or failed to offer an utility to the company for the emergency use of their check after the company issued up to date steering earlier this month. Many extra exams stay in regulatory limbo, nonetheless. Greater than 200 firms and laboratories are awaiting approval from the FDA for his or her exams as of this week, in response to the company’s web site.

Whereas all of this may be irritating, it’s essential to recollect how far the science has progressed in such a brief time period, says Saag. “It’s anticipated when you may have a brand-new illness and brand-new exams that there are many questions concerning the accuracy of the exams and their efficiency traits in massive populations,” he says.

It’s an unprecedented time, Hsu says. “We’re racing to develop good exams on the similar time we’re racing to know the underlying biology.”

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