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Much about the COVID-19 pandemic is changing, including how it’s treated and how we react to the virus’s presence in daily life. But one major recent change has epidemiologist Dr. Michael Osterholm concerned. On an episode of his podcast, he issued some warnings about a key tool for gauging the spread of the pandemic—the way it’s changing may make it harder for experts to measure how quickly COVID is spreading, and for people who are infected to know when to seek care.
Shift In Testing Makes It Harder to Measure Pandemic
Because many people learning they have COVID via at-home rapid tests, we no longer have an accurate idea of the extent of surges, said Osterholm. “Many individuals that test positive using a rapid antigen test do not get the results confirmed using a PCR test,” he said “This means that their case will go unreported and not included in the rates of daily cases we use to assess the state of the pandemic.”
At the same time, many states and localities are cutting back on free PCR testing. His prediction: “This under-reporting issue will only worsen and daily cases will no longer be an accurate way to assess the level of transmission in a given community.”
Rapid Tests Not As Accurate
“Rapid antigen tests are far less sensitive than PCR tests,” explained Osterholm. “Though they’re good at detecting the virus in patients with high viral load, they can still produce false negative results in patients that are infectious and at risk for severe disease. They may be better than nothing, but they are not an adequate replacement for PCR tests.”
Hospitalization Data Is a “Lagging Indicator”
“This is causing us to shift towards using hospitalization data as our means of surveillance,” said Osterholm. “The problem with this, of course, is that hospitalization is a lagging indicator. Today’s hospitalization numbers are not reflective of today’s transmission levels. They are reflective of the level of transmission days to weeks ago. This means that public health decisions made in response to a rise in hospitalizations will go into effect a few weeks after they are really needed, forcing us into a reactive public health strategy rather than a proactive one.”
Rapid Tests Don’t Indicate Infection
“Testing is only an indicator of whether or not someone has COVID at a point in time,” said Osterholm. “It does not mean that they won’t test positive again in 24 hours and their negative test in that moment, particularly with a rapid test, does not even mean that they are not infectious at the time the test was taken.”
He cited an example of a holiday party in Sweden in which attendees were required to have a negative rapid test one or two days before the event. That party still became a super-spreader situation, as 59% of party attendees were infected with COVID. “No matter how accurate a test is, it is not a substitute for primary prevention,” he said.
“False Security” A Risk
“If we cannot provide the population with timely and accurate tests, if we continue to make PCR testing less accessible for more of the population, we will likely see even fewer patients getting treated for COVID in a timely manner, more reliance on lagging indicators to determine the level of transmission in the community, and even more feelings of false security as people promote the use of these tests as a strategy for preventing COVID-related illness.”
