COVID-19 Testing: What It Measures, Who Gets it, and How Much Is Needed
Feature Story
Last update April 28, 2020
Jill Taylor likened the COVID-19 testing conundrum throughout the country to baking cookies without having all the ingredients. “Some places are missing flour, some are missing eggs, and some are just missing ovens,” said Taylor, who is director of the Wadsworth Center, New York State's public health reference laboratory.
During the National Academy of Medicine and American Public Health Association’s fifth COVID-19 Conversations webinar, held on Wednesday, April 22, panelists discussed COVID-19 diagnostic and antibody testing, exploring what these tests are trying to measure, the challenges of deploying them — and how to do so with underserved populations in mind.
While some states have the basic ingredients to deploy tests — including swabs and protective equipment for providers — others are facing infrastructure issues, said Taylor. In some cases, they don’t have a means to transport the tests or the capacity to process them quickly. Or, they’re racing to build drive-thru COVID-19 testing centers to avoid hospital-based testing. But even if they build them, people still may not come.
Expanding Testing Access — Location Matters
“Simply having an insurance card does not mean having access to health care,” said panelist Georges Benjamin, executive director of the American Public Health Association. “Where the testing facility is located makes a big difference, and quite often, they are not located near minority communities. And if you don’t have a car, you may not be able to get a walk-up test. Other barriers to testing access, Benjamin noted, include long lines, which may seem counterintuitive to physical distancing measures, and difficulty getting time off work.
Panelist Ashish Jha, director of the Harvard Global Health Institute, also cautioned that getting tested may be a source of fear, or in some cases, a marker of privilege. “I worry that knowing whether you are immunologically positive or negative will become a status symbol. We saw that in the early days, when NBA players were getting access [to tests] when really sick people couldn’t,” he said.
Asking the Right Questions — What Different Tests Mean
Before implementing wide-scale testing, it’s important to define what questions the tests will answer, said webinar moderator David Relman, professor of microbiology and immunology at Stanford University. Until those questions are defined, we won’t know how we should be deploying the technology, framing studies, or interpreting the data, he said.
“Do we want to know who is contagious or will be? Who is sick and destined to need a ventilator? Who’s resolving their infection and likely to become immune? We’re not there yet,” said Relman, “but that kind of capability would be really impactful.”
Testing for the virus and testing for immunity are also two very different things, the panelists emphasized.
COVID-19 diagnostic tests, which require a nose or throat swab, look for viral RNA; whereas antibody tests (also known as serology tests) check a person’s blood for evidence of an immune response to the virus. This can be found in asymptomatic people or those who have already recovered from the disease. However, reports of high rates of false-positive and false-negative results are delaying widespread antibody testing.
A positive result from an antibody test is not equivalent to immunity, noted Jha. Someone with a positive result won’t necessarily be able to return to work and life as usual, he said.
Taylor, the New York State lab director, added that the timing of test collection is also crucial. She described frantic calls from people who learned they were exposed to an infected person half an hour ago, and wanted a test immediately. “Getting a test right away does not allow time for the virus to replicate, so you won’t get a meaningful result. We advise waiting a few days.”
Is There a ‘Magic Number’ of Tests?
By some estimates, said Jha, the United States would need to test 500,000 people per day. That’s assuming all symptomatic people are tested, and that their contacts have been traced and subsequently tested as well.
Relman added that once cities and counties have a test for every person, they’re not exactly “done” with testing. It’s important to think about testing not just in terms of symptoms, but in terms of exposure level.
“We may have to do frequent testing and retesting of the same people, for example, health workers and others who work in high-exposure environments — your grocery store workers, your bus drivers,” said Relman. “We’re going to have to look at the potential and frequency of reinfection.”
A Moment of Reckoning for Health Information Sharing
When states are “up and running” with the number and quality of tests they need — and the financial and logistical support to sustain testing — the next phase is information sharing.
“I hope the COVID-19 pandemic pushes our health care system to be more integrated, and move away from the notion of blocking data from competitors,” said Jha.
Benjamin agreed. “We can get money out of an ATM machine 24/7, yet we can’t exchange basic info about sero-positivity across our health care system,” said Benjamin. “We need to build a national surveillance system that gives us real-time information.”
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