New tests could help Miami-Dade target communities where coronavirus hits hardest

Miami-Dade plans to use targeted blood tests across the county to track the spread of coronavirus in an effort to get a broader picture of how to respond to the outbreak.

Mayor Carlos Gimenez said this week the county has access to new pinprick tests that detect the antibodies in blood that indicate someone has the disease or has recovered from it. Results can be ready in 15 minutes, and subjects will be chosen at random each week based on demographic data.

“We expect by next week to get 10,000 new kits that will be used to do a demographic study on the spread of this virus in our county,” Gimenez said in a video message Wednesday.

The effort would make Miami-Dade one of the first counties in the country to launch broad surveillance testing for COVID-19 exposure.

While federal regulators aren’t yet endorsing blood tests alone to diagnose COVID-19, the method is increasingly seen as a welcome second choice to the “gold standard” nasal-swab tests that are in such short supply across the country, said Erin Kobetz, the University of Miami cancer researcher helping Miami-Dade plan the emergency sampling effort.

Because the tests detect antibodies produced as the body fights coronavirus, the analysis may not register positive for someone in the earliest stages of COVID-19 infection, she said. Kobetz said positive results from the blood samples are reliable enough that subjects would be instructed to self-isolate.

With 500 to 700 samples a week planned, Kovitz said the data will quickly trigger warnings to volunteer test subjects that they have contracted COVID-19, the disease caused by coronavirus. The overall results also will help Miami-Dade decide where to focus quarantine efforts, deploy more testing and offer some clues about the impact of social-distancing measures,

“It’s really wrap our arms around the local epidemic, and then make operational decisions based on that information,” said Kobetz, a professor at UM’s medical school and associate director of the Sylvester Comprehensive Cancer Center. “This effort quantifies the problem.”

Kobetz said the information could help cities decide whether to implement stricter coronavirus measures to respond to a cluster of cases, or for the county to weigh where to focus drive-thru testing options.

Surveillance testing for coronavirus in Miami-Dade

The strategy is known as surveillance testing, and is the centerpiece of a plan by President Donald Trump to plot the future of social-distancing and business closures implemented locally and at the state level to slow the spread of coronavirus.

In a letter to governors Thursday, Trump said his administration planned to begin categorizing counties as high, medium and low risk by using a dramatic expansion of surveillance testing to chart local levels of coronavirus. Those designations would help state and local leaders in “making decisions about maintaining, increasing or relaxing” restrictions to slow COVID-19 spread.

Miami-Dade’s surveillance kits involve serological testing for use of blood samples. The Federal Food and Drug Administration issued guidance March 16 saying it didn’t object to companies producing serological testing for COVID-19 as long as recipients are warned that the tests aren’t FDA approved and should not be the sole basis of a diagnosis.

Though the blood tests can miss some early-stage COVID-19 infections, Kobetz said the county’s study will use statistical adjustments to account for “false negatives” in tracking the spread of the virus. She said the lack of traditional COVID-19 tests requiring nasal swabs and lab processing leaves no option for a broader look at the pandemic’s reach. “We’re likely testing one out of 11 or 12 people who are infected,” Kobetz said.

The Miami-Dade project also could put Florida’s most populated county on the leading edge of a global effort to track how many people are immune to COVID-19, the disease caused by coronavirus. For people who catch the virus and show little or no symptoms, their silent bout with COVID-19 could leave them protected from a second exposure.

Widespread resilience to the disease, known as “herd immunity,” would provide a turning point in the spread. Identifying people who have already contracted COVID-19 without knowing it could help narrow the scope of defensive, social-distancing measures.

“Right now, the only weapon we have is to hide. Stay away from people. Hide from the virus,” said Dr. Michael Lauzardo, a professor at University of Florida’s medical school who is assisting with a planned long-term study of blood samples at the school’s home base in Gainesville and in the Villages retirement community. “We have to start thinking about herd immunity. ... You can’t shut down forever.”

“You need science,” he said. “You need evidence.”

Miami-Dade plans to use demographic data to randomly select participants that would offer a composite look at the county as a whole.

“It is like taking a poll to estimate the actual level of community spread,” said Dr. Aileen Marty, a professor of infectious disease at Florida International University. “It’s a good idea.”

This story was originally published March 26, 2020 at 6:17 PM.