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State Public Health Lab begins antibody testing

The state’s public health laboratory has begun antibody testing for COVID-19 to help public health officials track statewide exposure to the coronavirus.

Antibody testing, also referred to as serology testing, detects the presence of antibodies that indicate someone has been exposed to the virus causing COVID-19. The body produces antibodies to fight off such infections.

“Virginia’s public health laboratory plays an important role in our commonwealth’s COVID-19 response,” Department of General Services Director Joe Damico said in a news release, “and antibody testing is another tool we can use to not only fight the disease but to gain a better understanding of how it is impacting our citizens.”

As of Aug. 27, more than 1.5 million people have been tested for COVID-19 through a molecular test called a polymerase chain reaction, or PCR, which detects the virus’s genetic material and shows if a person is currently infected with the virus.

An additional 121,687 people have received an antibody test.

“It is necessary to have a full picture of the breadth of the disease when we are working to determine where the disease is traveling and where to target resources,” said Marilyn Freeman, the deputy director of DCLS and leading the lab’s antibody testing efforts. “PCR tells who is infected now but doesn’t show everyone who has been infected. The antibody test fills that gap. It can’t be used for diagnosis, but it can be used for surveillance to see how many people have been exposed.”

As the state’s public health lab, the Department of Consolidated Laboratory Services is usually the first in the state to begin testing for new and emerging public health threats like viral or bacterial diseases.

While there are private labs that offer antibody testing to help people understand if they have been exposed to COVID-19, the state lab will be working with public health officials to determine what people to test to better understand how the virus is spreading in the state.

The state lab began using the PCR test, to show if someone is currently infected with the virus, on Feb. 29. When other labs take over diagnostic demands of testing for the state, the state lab begins the surveillance process to track the impact of the virus on people in the state.

Scientists at the state lab are using testing that looks for IgM, or immunoglobulin M, antibodies, the ones the body makes when it fights a new infection, which is found in blood and lymph fluid. It will also be looking for IgG, or immunoglobulin G, which is the most common antibody and is in the blood and other body fluids and offers protection against bacterial and viral infections.

The Centers for Disease Control and Prevention notes that both antibodies can arise in serum within two to three weeks after the virus appears and says that detection of immunoglobulin M is uncommon without immunoglobulin G.

The state lab says that the presence of antibodies without a documented case of being sick can be used, potentially, to determine asymptomatic virus carriers — people who have antibodies in their blood but do not experience symptoms.

The serology test used at the state lab can process a large number of samples and get results in about 20 minutes, testing up to 220 samples per hour if necessary.

The state lab said it has a large inventory of testing supplies and does not anticipate supply shortages “at this time.”

“I think in the future, this test will support understanding of vaccinations,” Freeman said. “Research is going on now to see if the presence of antibodies offers long-term immunity from the virus, so we hope our results will contribute to that understanding.”

The state department of health began the Coronavirus Serology Project in June and partnered with a health system in each of the state’s five health planning regions, including Sentara Healthcare in the Eastern Region. There were 1,000 people who participated in each region, and each person completed a short questionnaire and had a blood sample taken. The University of Virginia did the lab testing for the antibodies.

In a briefing last month, state health commissioner Dr. Norman Oliver said about 2.4% of the 3,775 people who had enrolled in the study had antibodies to COVID-19, but said the prevalence of antibodies in the Latino community is much higher. He said the vast majority of people are still vulnerable to infection from the virus.