Virginia state lab begins antibody testing for COVID-19

Virginia Health Commissioner Dr. Norm Oliver, flanked by Gov. Ralph Northam, left, also a doctor, and Secretary of Health Dr, Daniel Carey, right, spoke at a news conference on Capitol Square in March. (Ned Oliver/Virginia Mercury)

Virginia’s state public health lab in Richmond began antibody testing for COVID-19 on Thursday, according to a news release from the Department of General Services, the agency that oversees it.

The Division of Consolidated Laboratory Services has offered polymerase chain reaction, or PCR, testing since Feb. 29, when it first validated the COVID-19 test distributed to states by the federal Centers for Disease Control and Prevention. PCR is a molecular test that can diagnose active cases of the virus by amplifying its genetic sequence in patient samples — usually taken from the nose or throat. 

Antibody testing uses blood samples to search for proteins that develop in response to an infection. The tests can’t diagnose active cases of the disease, but can determine if a patient has been infected with it in the past.

For the first six months of the pandemic, DCLS has relied solely on PCR testing to diagnose COVID-19 on a limited basis. The state’s testing protocol was originally limited only to patients with close contact to a lab-confirmed case or symptomatic individuals who tested negative for other respiratory diseases. That criteria has loosened as testing has become more widely available, but testing through the state lab is still limited to patients vetted by the Virginia Department of Health. Much of the lab’s capacity has been used for widespread screening at congregate care facilities such as nursing homes and prisons.

The lab’s newly-established antibody testing will serve a different purpose, according to the release. DCLS will use the tests to assess the spread of COVID-19 across Virginia and how many residents have been exposed to the disease. 

“PCR tells who is infected now but doesn’t show everyone who has been infected,” DCLS Deputy Director Marilyn Freeman said in a statement. “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.”

Antibody testing has been commercially available since at least May, but DCLS initially kept its focus on PCR testing to support other diagnostic labs and “mak[e] sure public health officials had the information they needed about active infections,” Dena Potter, a spokeswoman for DGS, wrote in an email on Thursday.

“Now molecular tests are more widely available across Virginia, so we are adding the antibody testing to help with that broader picture of current and past infection to help public health officials better understand how the virus is circulating in the state,” she added.

The state lab is using the Siemens Atellica IM COV2G — one of the first serology tests that display an estimate of the antibody levels in a patient’s blood, according to the federal Food and Drug Administration. In its release, DCLS said the presence of antibodies without signs of disease could potentially be used to identify asymptomatic carriers of the virus.

The antibody testing device is high throughput, with the ability to process up to 220 samples an hour. “The team has a large inventory of testing supplies and does not foresee issues with supply shortages at this time, as have been experienced by some labs for molecular tests,” the release continues.

Potter said antibody testing would be conducted in addition to current PCR testing. The lab can currently process up to 1,200 PCR samples a day. And like PCR testing, any patient who receives a serology test through the state lab will have to be approved by VDH.

“Information from serology tests can be used to guide control measures by knowing where the virus has traveled and who is more likely to be infected (i.e. men vs. women, age, race, ethnicity),” Potter added.

Virginia has already embarked on a COVID-19 prevalence survey using antibody testing with help from university partners. Early results indicate that roughly 2.4 percent of Virginians have been exposed to the virus, according to state Health Commissioner Dr. Norman Oliver.

Earlier this month, VDH also partnered with George Mason University and Inova Health System to study the prevalence of COVID-19 among children in Northern Virginia using serology testing.