How Well Do COVID-19 Antibody Tests Perform?

In early May, the U.S. Food and Drug Administration had approved the first coronavirus antigen test to check for previous infection. Since then, numerous companies in the world have mass-produced various kinds of serological tests. In a new study, scientists ranked 13 of the top-performing tests.

A team from NSF International and Novateur Ventures published their study in the Multidisciplinary Publishing Institute (MDPI) journal. Choosing among hundreds of antibody tests around the world, they ranked 13 different tests and how well each performed.

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While researchers are still testing and creating vaccines, doctors have tried several drug therapies for COVID-19 including anti-malaria pills and remedesivir, which have not been 100% effective for patients. To control the spreading of the virus while quarantine is slowing lifting around the world, reliable antibody tests are vital as a public health policy.

'Granting FDA Emergency Use Authorization to several companies to accelerate the manufacturing of diagnostic tests was a good move,' said Abdi Ghaffari, and advisor for Novatur Ventures and professor at Queen's University. 'But it must be accompanied by informed and clear guidelines on preferred and minimally acceptable profiles of the COVID-19 antibody tests designed for a specific indication.'

Various Types of Tests

Although all antibody diagnostic tests were designed to show people if they had been previously infected by the virus or not, the commercial tests have not been made under the same standards. The assay tests vary from using a 15 ELISA kit, a test using enzymes, to the RDT, or a rapid diagnostic test similar to the one used for malaria.

'No single assay can be used for all diagnostic use cases in the COVID-19 response for a country,' said Robyn Meurant from NSF International. 'What works well in one setting may be inappropriate or not accessible for another. As such, access to information on test performance, that is generated independently, greatly assists countries in informed decision-making.'

The team expressed the need for ongoing evaluations of all commercialized diagnostic tests because some are high performing while others have inaccurate results. In the study, thirteen tests were evaluated for their sensitivity and specificity.

The sensitivity of the coronavirus antibody tests is its ability to identify who is positive with infection. The specificity is the test's ability to identify those who do not have an infection with an accuracy greater than 95%.

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Importance of Testing

Several epidemiological studies assessing the spread of infection in China have stated that up to 86% of the positive coronavirus cases were undetected due to the lack of testing. Antibody tests can also detect if a person is asymptomatic.

Most of the molecular tests are highly accurate with detecting viral RNA molecules in people. However, it cannot distinguish if a person is highly infective.On the other hand, antibody tests can detect if the person has immunity to the virus as the test detects markers of the immune system response. The team concluded that the most effective testing would be to combine both molecular and antibody tests.

'Antibody testing is important to understanding the extent of exposure for COVID-19 so it can be effectively monitored and treated," said Ali Ardakani, the founder of Novatueur Ventures. "It is important for regional and national governments to continue their coordinated efforts to independently validate antibody test performance and also partner with industry to scale up manufacturing and production capacity.'

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