Hands holding antibody tests

Living with a COVID-19 patient? You probably have antibodies

If someone in your household has had COVID-19, you’re very likely to have antibodies against the virus – even if you didn’t experience any symptoms yourself.

That’s what the early evidence from SCAN, a research program undertaken by Weinberg College biological anthropologist Thomas McDade and a team of Feinberg School of Medicine researchers, seems to suggest.

SCAN stands for Screening for Coronavirus Antibodies in Neighborhoods, and that is exactly what McDade and his Feinberg School colleagues are doing.

Their goal is to determine why some neighborhoods and populations, like African-Americans and Latinos, are being harder-hit by the pandemic than others.

The team is taking an innovative approach. Rather than prompting members of a community to venture to a testing center, they are encouraging participants to sign up for a test via a website. The test kit is then mailed to the participants, who extract a drop or two of blood from their fingers via a finger prick and dab the blood onto specially designed paper. The participants then return the kit to the SCAN team’s lab, where it is tested for coronavirus antibodies.

“Our approach combines the convenience and safety of at-home blood collection with the quantitative rigor that is possible in the lab,” McDade says.

‘Intra-household transmission’

The team initiated the project in late April, and soon received a RAPID grant from the National Science Foundation to accelerate their research. After formally launching the program in mid-June, they now have their first results. And one of the early findings that strikes McDade as particularly interesting is a surprisingly high rate of “intra-household transmission.”

“If you had someone in your home with a confirmed case of COVID-19, the chances that you test positive — based on antibody levels in your bloodstream — are greater than 80 percent,” McDade says. “Most of these people who tested positive never had symptoms, or if they did, they were mild. So it shows how the virus can spread, even in the absence of clinical infection.”

The team has analyzed about 300 samples thus far, and plans to ramp up to at least 3,000 tests over the next two months.

“Our aim is to screen people in the community for antibodies to determine if they have been exposed to SARS-CoV-2,” McDade says. “This is particularly important given how many people have mild or asymptomatic cases. We can then investigate the individual-, household-, and community-level factors that predict viral transmission.”

The COVID-19 antibody tests that have been commonly used thus far have been notoriously inaccurate, providing false results up to half the time, according to the Centers for Disease Control. But McDade says the SCAN test is different in that it is a lab-based test, rather than the more common lateral-flow assay tests. Those tests yield a binary result — positive or negative — and are fast, but less sensitive and accurate.

“This was particularly the case with coronavirus testing early in the pandemic, when a lot of poor-quality tests were rushed to the market, giving the whole antibody testing enterprise a bit of a black eye,” he says. “Our test is very accurate — as accurate as the gold standard protocols that use serum from venipuncture.”

Seroprevalence

McDade says the SCAN team’s method seems to be working well thus far. “People are willing and able to stick their own fingers, put a couple drops of blood on filter paper, and send the sample back to the lab where we can quantify antibody levels,” he says.

Early results indicate that “seroprevalence” — evidence of exposure to SARS-CoV-2 in the form of antibodies in the blood — is higher than in previous reports. But McDade says that has a lot to do with his early sample set, which includes a large number of healthcare workers. “This is not a big surprise, given that these workers are more likely to be exposed,” he notes.

Given the project’s accessibility and accuracy thus far, it wouldn’t be surprising to see members of the public lining up to request a SCAN test. Unfortunately, due to funding constraints, SCAN isn’t able to expand the testing beyond the initial target groups.

“SCAN is a research study, not a public health or clinical testing service,” McDade explains. “While the research will be done with the general public, we will be restricting the sample to individuals that fit with our research goals.”

That means that at the moment, only those in the age groups, neighborhoods and other categories that SCAN is examining will be able to procure this antibody test.