Florida health officials recently asked labs reporting COVID-19 cases to include a new data point: how long it took for the specimen used in the test to register as positive, a measure that can indicate how much virus is present.
The directive from the state, quietly issued in a memo to labs from the Florida Department of Health in early December, is worrying some public health experts who say the new information, if shared with infected people with perceived low amounts of virus, could prompt them to go back into public too soon, and spread it.
“This could be the next public health disaster in Florida,” said Aron Banks, whose Doral-based company CardioPath shifted its lab toward testing for COVID-19 early in the pandemic.
Banks said his main concern is that a result signifying less virus might actually represent an infection that is growing, not waning, meaning the person could become much more infectious in the days after the sample was given. That is especially worrying for small, independent labs who don’t know if they’ll be held liable for sharing the information with their clients.
“You’re telling somebody that you might be safe to go out in public, and then they’re transmitting,” he said. “There are still a lot of things we don’t know.”
Another question for some health experts: Could the new information be used by the state to disqualify some test results as not being considered real infections, reducing the state’s official case counts?
But there also are potential public health benefits. The information could be used to prioritize highly infectious people for contact tracing, health experts said. And it could shed light on growing outbreaks, measuring how fast they are spreading and where, said Stephen Kissler, an immunology and infectious disease expert with the Harvard T.H. Chan School of Public Health.
“You can get a very good monitor of where cases are likely to head just based on a single snapshot in time,” Kissler said.
The tests aren’t authorized to measure what the state has asked. They are designed — and approved on an emergency basis by the U.S. Food and Drug Administration — to show whether the virus is present at all, not how much of the virus is in a particular sample.
The state hasn’t offered any real explanation of why it is now asking for the information. A spokesperson for the Department of Health provided the memo sent to the labs last month but wouldn’t explain it, saying only that the agency wants labs “to provide this information to the department as a part of our collaborative efforts to combat this virus.”
Not all testing equipment being used in Florida labs will produce the additional information, which measures the “cycle threshold” in a molecular test, or how many runs it takes to amplify the virus to a point of detection.
Some of the commonly used testing platforms in the pandemic, including the one used by Banks’ lab and Baptist Health of South Florida, the region’s largest nonprofit hospital chain, don’t measure cycle threshold counts, only registering negatives and positives.
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At Baptist, that’s because the data “doesn’t provide additional enhanced clinical information,” a spokesperson said.
Rachel West, a postdoctoral associate with the Johns Hopkins Center for Health Security, said not only are the tests not authorized to quantify how much virus is in the sample, but that a host of other factors, including the method used to collect the sample and how it is stored, could throw the metric off.
To use the data to accurately detect how much virus is in a sample, West said, “you have to do that experiment separately for the specific test you are using.”
Despite those limitations, Kissler, the Harvard immunology expert, said he was encouraged by the Florida Department of Health’s efforts to get more data and share it. He added that he would hold that view even if health officials used the data to scrutinize and disqualify some lower-virus cases, assuming that they instead prioritized higher-virus cases for contact tracing.
Kissler said that public health experts haven’t done a good enough job explaining that not all positive test results mean the same thing for COVID-19. If the objective is to find everyone that has the virus in their body, regardless of whether they are spreading it, then every positive should count equally, Kissler said. But if the goal is to halt the spread of the virus, he added, then more nuanced information is needed.
“It does open up the possibility of saying, ‘Maybe we should just ignore everything with a [lower viral load],’ " Kissler said. “While that would reduce case counts, maybe that is merited. Maybe we are most interested in cases with [higher viral load].”
Not all experts share that view. Gigi Gronvall, an immunologist who also works at the Center for Health Security, said the data is only appropriate in a research setting, and there’s no public health value in reporting it.
“From the perspective of a governor who is looking at a whole bunch of data, the value is in the general trends,” Gronvall said.
Those trends can include assumptions about a certain number of false positive and false negative results, she added.
“We may all want to have perfect knowledge of what’s going on beyond the test, but as far as what we can know, it just seems like an unnecessary burden for this to be reported,” Gronvall said.
Banks, the lab owner, worried that the information, if shared with patients, could cause “mass confusion.” He helps run the lab at his Doral company and said he has tested more than 50,000 samples since the pandemic began. He said he couldn’t fathom what health officials were driving at with the directive.
“I have never been one to go off on a conspiracy tangent because, as a scientist, I want to be evidence-based on everything,” Banks said. “So I don’t know what the governor’s end game with [the new metric] is, but you can’t fudge science.”
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