Why does one Chicago ZIP code have more COVID-19 cases than the next? Finger-prick blood tests may help find a - Chicago Tribune

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Northwestern University scientists will be asking Chicagoans to prick their fingers and send in a dried blood sample as part of an effort to figure out why some parts of the city are hit so much harder by COVID-19 than others nearby — research they hope could help control future disease flare-ups.

The blood tests for COVID-19 antibodies, also known as serology testing, will be conducted in five pairs of adjoining city ZIP codes initially. Each pair includes an area with much higher infection rates than its neighbor, as determined by city data from the end of April that is based on traditional coronavirus tests.

COVID-19 study

For example, the study is comparing the 60612 ZIP code, which includes the Near West Side and had an infection rate exceeding 1,000 cases per 100,000 people, to 60622, which includes Ukrainian Village and had an infection rate below 644 per 100,000. Researchers will also collect web-based surveys of the participants and analyze other data.

“The numbers are shocking,” said Thomas McDade, the biological anthropologist leading the effort at Northwestern. “So why is that?”

Thomas McDade, a biological anthropology professor at Northwestern University, holds blood samples from research participants in a study for coronavirus antibodies.

Thomas McDade, a biological anthropology professor at Northwestern University, holds blood samples from research participants in a study for coronavirus antibodies. (Jose M. Osorio / Chicago Tribune)

One possibility, McDade said, is there’s just more virus present in some neighborhoods. Another is that the virus is present in equal proportion but it spreads more rapidly or is more likely to be fatal because of socioeconomic differences, prevalence of preexisting conditions and lack of access to health care.

“But there’s no good way to answer that question unless you get out and do some serology and find out just how many people have been exposed, because there are so many cases that never get registered because people don’t get an actual test or are asymptomatic,” said McDade, whose team includes Northwestern doctors, a pharmacologist, a psychologist and others.

Recently, the federal Centers for Disease Control and Prevention estimated that infection rates in the United States were 10 times higher than previously known, a conclusion based on antibody test results from across the country. The agency estimated 23 million U.S. residents have been infected.

Most antibody tests are conducted by drawing blood in a lab, but McDade and his team are turning to a method he has used for decades in anthropology. Instead of a traditional blood draw, kits will be mailed to the 3,000 or so participants that allow them to prick their finger, place a drop of blood on filter paper to dry and send in the resulting sample.

It’s the same protocol that has been used since the 1960s to test newborns for genetic diseases with a prick to the heel, and it costs only about $1 to collect each sample, McDade said. It also will allow people to conduct the tests safely in their own homes, he added.

The tests Northwestern is using are better at detecting lower levels of antibodies than most of the commercial antibody tests on the market, said Dr. Elizabeth McNally, director of the Northwestern University Feinberg School of Medicine Center for Genetic Medicine. That will help detect cases where the person wasn’t severely ill or had no symptoms. The method is also “much more sensitive” than the tests used by the CDC, she added.

“We want to know what percentage of people look like they’ve had exposure, that their bodies developed some kind of immune response to this,” said McNally, who’s part of the research team. “And then really importantly, we want to ask how these people do over the next three months, six months and beyond. ... Do a bunch of these people actually get sick going forward in the future, or do they stay relatively well?”

The 3,000 anticipated participants, who will be identified through social media and neighborhood organizations, will be asked to fill out surveys to identify potential contributing factors, such as social-distancing and mask-wearing practices, as well as whether participants used public transportation, had to leave home to work or had kids in day care. People can apply to participate online through a dedicated website.

McDade and his colleagues hope that the results of the study, which could be completed before summer’s end, will help inform public health policy in time for a potential second wave of infections in the fall.

“You just think about what we did nationally and in Illinois three months ago, it was a sledgehammer approach,” McDade said. “We shut everything down and made everyone stay home.

“And now we’re starting to open up. So what if we get a spike in infections? Do we bring out the sledgehammer again, or can we bring out a scalpel and identify the things that are most effective at mitigating the chance of transmission and just implement those.”

Secondarily, the study also will try to determine whether the dried blood samples can be used to detect “neutralizing antibodies,” which are different from the “binding antibodies” commonly now identified through COVID-19 serology tests.

Binding antibodies work by attacking a virus that has already infected someone and may diminish more quickly than neutralizing antibodies, which prevent the virus from invading the cells in the first place. McDade said the presence of neutralizing antibodies might be a better indication that someone is truly immune from the disease.

The study is funded with a $200,000 grant from the National Science Foundation.

Here are the initial five sets of ZIP codes that will be studied, and the neighborhoods to which they roughly correspond, listed with the harder-hit ZIP codes first:

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· 60645 (West Rogers Park) and 60660 (Edgewater)

· 60639 (Belmont Cragin) and 60647 (Logan Square)

· 60612 (Near West Side) and 60622 (Ukrainian Village)

· 60609 (Back of the Yards) and 60615 (Kenwood)

· 60655 (Mt. Greenwood) and 60643 (Beverly)

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