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By Meredith Cohn 
 Plenty of people want to know whether they ever had COVID-19, and public officials need to know. But existing antibody tests that look for markers of the disease caused by the coronavirus have not met the challenge, with accuracy, cost and convenience problems.
 Scientists at the Johns Hopkins University and elsewhere, however, are working on the next generation of these tests that can be done at home.
 "We wanted to develop something you could use on your kids," said Netz Arroyo, a Hopkins assistant professor of pharmacology and molecular sciences who joined with a biomedical engineer and a biophysicist to repurpose a common medical device to look for the virus.
 "It would be easy and you may not even have to poke their finger every time," he said. "Now you have to go to a lab and have a blood draw."
 Antibody tests are different from the diagnostic tests widely used to confirm COVID-19 cases, which involve a nose swab being sent to a lab for analysis.
 The Hopkins group designed its antibody test using a glucose monitor, a tool already used by millions of diabetics at home to keep tabs on their sugar levels using a finger prick of blood.
 The test can use a drop of blood, saliva or maybe other bodily fluid on a paper test strip that is inserted into a container and then into the monitor. If there are antibodies present, it sets off a series of chemical reactions. The monitor still reads glucose, created by the chemical reaction caused by the presence of antibodies, and the level is proportional to the level of antibodies.
 Antibodies are proteins produced by a person's immune system in response to a virus. Their presence can indicate someone was infected recently, but do not indicate an active infection. They typically offer protection if they encounter the same virus again.
 That's not to say that a positive coronavirus antibody test promises someone immunity from another case of COVID-19. Scientists do suspect survivors of the disease have some protection, but they don't know how much or for how long.
 Once that's sorted out, antibody tests could prove someone has immunity and could return to school or work, Arroyo said. They also may be used to track the effectiveness of a vaccine.
 More immediately, the tests could identify hot spots that were not obvious from diagnostic testing alone. Health officials and scientists say many people with COVID-19 are not diagnosed with a lab-based PCR test or a rapid test in a doctor's office because they have no symptoms or mild illness and are not tested.
 The Hopkins test is proving reliable but is being refined still and won't be available until perhaps sometime next year. Arroyo noted that this mechanism can also be adapted for future outbreaks and pandemics.
 For now, there are 47 antibody tests with emergency use authorization from the U.S. Food and Drug Administration. Nearly all require individuals to visit a lab to have blood drawn.
 That has limited wide-scale use so far, though researchers have begun using the tests to assess the infection rates in certain areas.
 One recent study by Stanford University School of Medicine used blood samples taken from dialysis patients to determine that fewer than 1 in 10 Americans have antibodies to the coronavirus, with higher rates among Black and Hispanic people and those in densely populated areas.
 Other research projects are underway, including at Northwestern University in Chicago with the aid of a test developed there that, like Hopkins' test, relies on a drop of blood that could be collected at home. In that case, the blood is dried on a paper strip and mailed to a lab.
 Each costs about $1, a fraction of typical antibody tests at commercial labs that can range from about $40 to about $120.
 Work started on the Northwestern coronavirus test in April in the lab of Thomas McDade, an anthropology professor and a faculty fellow in the university's Institute for Policy Research. He said they have proved easy to use and reliable.
 Like the Hopkins tests, they show the level of antibodies, information that could show the severity of someone's infection but also could help scientists understand levels of potential immunity. Repeat tests could show whether antibodies and their protections wane.
 The Northwestern lab already has tested 1,000 samples and plans to get 3,000 to 4,000 from Chicago-area disadvantaged neighborhoods to show the rates of illness and death. An earlier study found 70% of people who lived with someone infected with COVID-19 also tested positive.
 "An individual infection is not super useful information ... though I understand people's individual level of curiosity," McDade said.
 "I can't tell you how many people have written or talked to me about that cold they had in March probably being coronavirus," he said. "They all come back negative, but a lot of people with no symptoms come back positive."
 He said the real value of the tests is the insight into hidden hot spots.
 Such tests will be crucial going forward since diagnostic testing has been lacking since the start of the pandemic, said Dr. Ravina Kullar, a spokesperson for the Infectious Diseases Society of America and adjunct faculty member at UCLA.
 Having more easy-to-use and reliable antibody tests, including those that show the level of antibodies, will help inform decisions about resources and mitigation efforts, she said.
 "All of these tests can be expensive, require you to go to a clinic or doctor's office, and cannot be done at the comfort of your own home," Kullar said. "Diversifying our testing in the U.S. can help with controlling this pandemic, so a test that can be done at home, like a pregnancy test or glucose monitor, to tell you if you may have had the SARS-CoV-2 virus or if you presently have it could be a game-changer."
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 PHOTO (for help with images, contact 312-222-4194): ANTIBODY-TESTS

Coronavirus antibody tests have had plenty of problems. A better, at-home version is in the works