A coronavirus antibody test that is more than 99% accurate is now cleared for emergency use in the US, easing concerns of false positives that hindered earlier tests

• A coronavirus antibody test that is more than 99% accurate has been authorized for emergency use in the US, the Swiss drugmaker Roche said Sunday.
• The test boasts a 100% sensitivity rating and a 99.8% specificity rating, which is much higher than many of the initial antibody tests to reach market, and could significantly reduce the potential for false positives.
• Antibody testing is considered a key step toward reopening the country, as it would offer a better understanding of how widespread the virus is and who may be immune to it.
• However, there has still been no definitive study showing having antibodies means people are immune from getting infected. Researchers also do not yet know how long-lasting any antibody protection is for this new virus.
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US regulators authorized Sunday emergency use of a coronavirus antibody test that is more than 99% accurate, addressing concerns about high false positive rates that have plagued some of the first tests.

The test is made by Roche, a Swiss giant in the pharmaceutical and diagnostics industries. Roche said Sunday it will boost its manufacturing to produce "high double-digit millions per month" of the test.

Antibodies are proteins created by the body's immune system to fight invading threats, like viruses or bacteria. Antibody testing is seen by many as a critical step into reopening the economy. Some have floated ideas of using the tests to issue some form of "immunity passports," which could allow people with the antibodies to return to work.

Roche stated the test has a 100% sensitivity rating and a 99.8% specificity rating, which are significantly higher than some of the first antibody tests that were cleared for use in the US. The results came from using more than 5,000 samples on its test.

It will take about 18 minutes to process a single test, with Roche's devices able to run up to 300 tests per hour in an automated fashion, the company said.

One recent study found several of these tests are less than 90% accurate. Combined with Roche's ability to mass-manufacture millions of tests, this new test should help address the issue of false positive results, where a test may tell someone they have the antibodies when they actually do not.

Another medical diagnostics giant, Abbott, has been using its antibody test for the past few weeks in the US. Abbot says its test is 99% accurate, based on testing about 1,000 samples.

Read more: Tests that can tell who's had the coronavirus are crucial to reopening the country. Here are the companies racing to bring them to the US healthcare system.

Even if fully accurate, antibody testing still faces several critical unknowns that may limit the usefulness of these tests.

First, it is not yet known for sure that having antibodies equals protection. For most viruses, having antibodies means being protected from future infections. But studies have yet to be done on the novel coronavirus proving this to be the case, and there have been some reports of potential reinfection.

Even if antibodies give a degree of protection from the virus, researchers do not know how long that protection will last. This could be another critical limitation if antibody protection lasts for months instead of years.

Finally, it is still unknown what percentage of the US or world population has already been infected with the coronavirus. Reliable and widespread antibody testing can help answer this question.