Gov. Ron DeSantis is pushing for more coronavirus antibody testing in Florida. He says the tests will help health officials have a better understanding of how the virus has spread throughout the state. But some experts have raised concerns about the accuracy of the tests.
DeSantis says he thinks Florida’s coronavirus numbers don’t fully reflect the number of people in the state who have gotten the virus.
"I’ve said before and I’m just going to stress that cases are simply detected infections. There are and have been way more infections than documented cases. So if you see 5,000 cases, or 10,000—just understand that is not the sum total of the people that have been infected,” DeSantis said.
DeSantis points to a study by the Centers for Disease Control and Prevention as an example. He says the April study focused on four Florida counties: Martin, Palm Beach, Broward, and Miami Dade.
“Based on the antibodies and the seroprevalence, CDC believes there were actually 11-times more infections at the time in Southern Florida. So that’s 17,400 infections that had actually occurred,” DeSantis said.
Seroprevalence means the number or ratio of people in an area who have been infected with a specific illness. The information is meant to help health officials better understand how the virus is spreading and could also give a picture of how many people in the state could be developing immunity to COVID-19. That’s why he says antibody testing is important. It’s the kind of test that looks to see if someone has had the coronavirus at some point in the past, not whether they’re sick right now.
“Some of these areas that have hit 15/20 percent, the virus doesn’t expand as much. So if you have a very low seroprevalence then its got more potential target to reach. I think it’s very important, not only as we get through this period, but as we get into the fall and the flu season, to have that source of information I think it going to be very, very important, so we want to work to get that done," DeSantis said.
Gigi Kwik-Gronvall is a senior scholar at the Johns Hopkins Center for Health Security. She recently coauthored a study on using antibody tests in conjunction with COVID-19. She says they can make sense on a population level, to help governments get better understanding of the virus.
“The main purpose for these kinds of tests right now is to do population studies, to do serosurveys, so that you can figure out what percent of the population has been infected, whether that is changing over time, so you can see if you’re changing public health intervention measures, if that’s working,” Gronvall said.
But for individual people, they’re not that useful, at least not right now. Gronvall says that's because of the potential for false positives and false negatives.
The CDC says coronavirus antibody tests can sometimes pick up antibodies from other viruses, including some that give people common cold symptoms. It also says some people who have gotten the virus might never produce antibodies. Health officials caution it’s NOT a good way to tell whether you would be able to spread the virus to others. But Gronvall says as health professionals learn more about the virus, there could be reasons in the future that antibody testing would start to make more sense for individuals.
“If we find out why there is a medical reason that’s important to know whether you have it or not, then that changes the approach. Then you would probably have multiple antibody tests, depending on the prevalence of disease, to make sure that you have an accurate result,” Gronvall said.
Gronvall says one example where it’s important to know whether you have antibodies from a virus is HIV.
"For HIV if you get a positive antibody test you absolutely, it’s really important for you to find out if that’s a real positive. You would get a couple of tests at once to find out if you’re truly positive. Because then if you’re positive, then you have a course of therapy that you need to start on,” Gronvall said.
But Gronvall says that’s not the case with the coronavirus. She says, at least right now, if someone tests positive for coronavirus anitbodies, there’s no “medical next step” that person needs to take.
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