1,000 frozen blood samples will help determine accuracy of RI antibody test

Coronavirus

PROVIDENCE, R.I. (WPRI) – Gov. Gina Raimondo announced last month that COVID-19 antibody tests have arrived in Rhode Island, but it could be weeks before they’re actually rolled out.

WPRI 12 spoke with Dr. Angela Caliendo, president of Brown Physicians and an infectious disease doctor at Rhode Island Hospital, about the tests and what needs to happen behind the scenes before people can begin to be tested. (Watch our full interview with Dr. Caliendo in the video below)

What are antibody tests?

Antibody, or serological, tests detect the presence of virus-fighting proteins called antibodies (in this case for COVID-19) in a person’s blood. This can tell doctors whether a person has been exposed to or infected by the novel coronavirus. 

Dr. Caliendo said these tests will not replace the current swab tests being done to identify a person with an active infection, since it takes about two weeks to develop antibodies. Instead, the tests will help health officials get a better sense of how widespread the disease actually is in the community.

“We need to begin to get an understanding of just how many people in the state of Rhode Island have been infected,” Caliendo said. 

We have the tests now, so why can’t testing begin right away? 

Before the tests can be rolled out to the public, the tests must be validated to ensure they’re accurate. 

Right now Caliendo and Dr. Jonathan Kurtis, chair of the Department of Pathology and Laboratory Medicine at Brown University’s Warren Alpert Medical School, are co-chairing a task force to design this validation study.

The goal is to understand how well the test performs. Caliendo said it’s important to ensure there aren’t a large number of false positives, which could result in inflated infection numbers and misleading information. 

In order to validate the test, Caliendo said they’ll likely have to test upwards of 1,000 samples, which could take weeks. 

Where do those samples come from?

Because Caliendo said it takes about two weeks for people to develop antibodies to COVID-19, the positive samples can come from people who tested positive for the virus at least 14 days ago. The R.I. Department of Health tracks everyone who’s tested positive for COVID-19 so far. 

The negative blood must come from people who are known to have never contracted COVID-19.

“The best way to do that is to go into the freezers in the clinical laboratory and take out specimens that were collected on patients before COVID even started, so back in the fall, last summer, when COVID wasn’t circulated,” she said. “So you know those patients couldn’t have been infected with the virus.” 

She said she is hopeful there will be enough frozen blood to generate roughly 1,000 negative specimens. 

“To do a good specificity study, which is to ensure that there aren’t a lot of false positives, you need a large number of samples,” she said. 

How accurate are these antibody tests? 

That’s something that Caliendo and her team are aiming to find out. According to the Department of Health, the state has purchased the SD Biosensor test. The company said it’s now tested about 444 samples, but had initially tested just over 60.

“The reality is there’s very little data out there,” Caliendo explained. “The company’s data had, I think, 35 or so positive specimens and 30 negative specimens. So it’s a very small sample, and it’s not a large enough sample to give you a good understanding of how the test performs.”

That’s why Caliendo and her team have to conduct such a large study. She hopes they can use the specimens they collect to validate tests from other companies as well. 

Caliendo said they could ultimately conclude the test doesn’t have a high enough specificity and recommend against using it. 

“Hopefully that won’t be the situation,” she said. 

What happens when the validation is done?

Right now, Caliendo said there’s another group working to determine how to deploy the test to ensure the state gets a truly random sample of people. A random sample will help health officials more accurately estimate how much of the population has been infected. 

Rhode Island has 20,000 tests to use. RIDOH spokesperson Joseph Wendelken said there is likely going to be a strategic way the tests are rolled out.

“The goal is to get a sense for the prevalence of disease in the community,” he said, adding that a specific plan should be released in the near future.

How the test is conducted is another question. In some places, samples of blood are being collected through fingersticks, but Caliendo said that might not be what happens in Rhode Island.

Currently, their plan is to validate the test using serum and plasma that’s collected through a traditional blood draw. “And whatever sample you use to validate the [the test], you have to use to conduct the test too,” she said. 

The more cumbersome process of drawing blood would likely need to be done in people’s homes or at draw stations, Caliendo explained, which might make it more challenging to get samples. She said they’re looking into obtaining devices that would allow fingerstick collection of serum and plasma that would typically be collected though a traditional blood draw. 

Some clinics are already offering antibody tests. Are they legitimate? 

“I don’t know what test people are using, but the big question everybody should be asking is, ‘Can I please see your validation data to see sensitivity and specificity?'” Caliendo advised. She said people should see a specificity of at least 98% or 99%, though she adds she doesn’t yet know if tests will hit that mark.

Caliendo said Lifespan’s clinical lab is currently offering an antibody test that requires the approval of an infectious diseases specialist in order to make sure it’s used in the appropriate clinical situations and properly interpreted.

“There is limited supply,” she said. “So [it’s] not widely available.”

If I get tested and I have antibodies, am I immune to COVID-19? 

“That is the million-dollar question,” Caliendo said. 

Right now scientists are trying to learn whether antibodies protect people from being re-infected by the novel coronavirus, and if so, for how long. 

“For some infections, antibody protect you from getting infected again,” Caliendo said. “We do not know if this is the case for COVID. We do not know that if you have antibody that you then won’t get the infection again. And so people have to be very careful if they do get antibody tested, and they find out that they are positive for the antibody, that doesn’t meant they are immune from getting infected again.” 

It also doesn’t mean you’re no longer contagious, Caliendo said.

“An antibody test is not a get out of jail free card,” she added. “You still have to be just as cautious as you would be if you either didn’t know your antibody status, or your antibody status came up negative.”

Watch our full interview with Dr. Caliendo in the video below.

Copyright 2020 Nexstar Broadcasting, Inc. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.

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