Testing is an essential part of resolving the Covid-19 coronavirus pandemic.
It’s essential to determining who has the virus, which can spread from people who may not exhibit any symptoms at all, sometimes for weeks. These unwitting spreaders are prolonging the pandemic, forcing the government to enact costly economic shutdowns. The way to relax these measures is to test people, sometimes repeatedly, and isolate the infected.
But since there still aren’t enough tests in the US to go around, who should be tested?
Current guidelines from the Centers for Disease Control and Prevention (CDC) put hospitalized patients with symptoms; health care workers and first responders with symptoms; and nursing home residents and prisoners at the top of the list — and people who don’t have any Covid-19 symptoms much lower.
However, some researchers say the focus right now should be on finding people with the virus who don’t have symptoms because they are driving new infections. People who are starting to experience fever, shortness of breath, and a loss of smell, they say, should not be tested and should be treated as if they are already infected.
It’s a debate that exposes the tension between treating individual patients and protecting the public at large. But it’s not a hypothetical; these are decisions that have to be made now. Experts estimate we should be deploying upward of millions of tests per day. Yet the United States is barely getting above 220,000 daily tests. And it’s forcing many health districts into the unfamiliar territory of rationing tests, forcing them to confront the prickly question of who does or does not get swabbed.
The number of tests and how they’re deployed will shape the trajectory of this pandemic.
The case against testing people with Covid-19 symptoms
There are several therapies for Covid-19 under investigation. Some, like remdesivir, are being used to treat patients under compassionate use guidelines or emergency use guidelines.
But right now, there isn’t a specific drug for Covid-19 for broad use, so a positive diagnostic test for the illness doesn’t change how most patients are treated. In other words, if you have symptoms, a diagnosis won’t affect how you’re treated by doctors.
In addition, by the time an infected person has symptoms like fever and breathing difficulty, the virus is often quite far into its replication cycle and may be in decline, so a diagnostic test may not even pick up the disease. And at that point, many of the symptoms stem from the body’s immune response to the virus, like inflammation and fever, rather than the direct damage from the virus itself.
France’s health minister Olivier Véran told the French broadcaster LCI on April 30 that testing people with symptoms wouldn’t have done much to control the pandemic.
“A test does not cure. A test doesn’t change the treatment. A test doesn’t change isolation [protocol],” he said. “If we had tested absolutely everyone, everyone with symptoms, we would have had more or less the same number of cases.”
Since it doesn’t make a difference in how patients are treated, Paul Romer, an economist at New York University, argues that testing such patients doesn’t make sense. Romer co-authored an article for the Atlantic with bioethicist Ezekiel Emanuel laying out his case for not testing patients with symptoms.
“To safely reopen closed businesses and revive American social life, we need to perform many more tests — and focus them on the people most likely to spread Covid-19, not sick patients,” wrote Romer and Emanuel.
Romer explained that by the time a patient has symptoms of Covid-19, the diagnostic test doesn’t provide much more useful information. For instance, a patient may show up with a very low blood oxygen saturation, fever, and congested lungs, and may have been exposed to someone else with Covid-19.
“Suppose you run the test. If it comes back positive, you’re going to treat it like they’re positive. If it comes back negative, you’re probably going to say ‘it was a false negative and we gotta presume this person is positive’ and do the same thing,” Romer said. “So what’s the point of the test?”
The better approach, according to Romer, is to presume that people with symptoms have the virus and are infectious. And rather than testing again to confirm the virus is gone, hospitals should establish a standard isolation period after the last date symptoms are present. (The CDC recommends 10 days of precautions after symptoms first appear and three days after recovery.) Those saved tests can then be deployed to trace the contacts of the presumed infected, some of whom might not have symptoms and could be contagious.
Those who test positive for Covid-19, even without symptoms, can then be directed to isolate themselves until the infection passes, limiting further spread of the disease. This pattern of repeated testing and isolation will eventually extinguish the pandemic.
The case for testing patients that have Covid-19 symptoms
That’s why some experts say we need to make sure critical resources, like personal protective equipment (PPE), are reserved for health workers dealing directly with the highly infectious virus. Some Covid-19 patients need to be treated for weeks, and everyone entering their room needs fresh protective gear every time they enter, so treating a single patient can consume a lot of scarce resources.
“Right now, we’re sort of in the midst of shortages of so many different materials around the country, and one thing our institution is really trying to do is save on PPE,” said David Pride, an infectious disease specialist at UC San Diego Health. “And to do that we’ve had to do a protocol where we are testing every single person that gets admitted to our hospital system.”
Pride added that another issue is that the isolation regulations around Covid-19 patients mean that they can’t see their families, which is a huge emotional burden. “If we can demonstrate through successive testing, meaning multiple rounds of testing, that they are not shedding the virus, they can come off of these precautions, which means that they can actually have their loved ones there,” he said.
Robert Atmar, an infectious disease physician at the Baylor College of Medicine, said that it’s also worth considering how the information from a test can be used for public health.
“The main question is how the health department responds to a positive test,” Atmar said in an email. If no contacts are being traced, then it might make sense to presume infections in patients to save tests. But if everyone who is presumed infected is traced, then contact tracers will waste valuable time and resources following the footsteps of people who may not have been infected.
Christine Mitchell, the executive director at the Center for Bioethics at Harvard Medical School, noted that while finding asymptomatic spreaders is essential to slowing the pandemic, identifying the infected can help limit the spread inside hospitals. For instance, testing can help determine whether someone can share a room with another Covid-19 patient. If they were uninfected, this could expose them to the virus and add new complications.
“I don’t know why it’s necessary to advocate not testing patients,” Mitchell said. “You do need to know these things to create a safe environment for patients as well as a safe environment for other patients.”
How should we prioritize Covid-19 testing for everyone else?
Aside from whether to test patients who have symptoms for Covid-19, most experts do agree on who else should be ranked high for testing, namely health workers and first responders on the front lines of the pandemic.
Doctors, nurses, and hospital staff face a greater risk of exposure to the virus, and because they are in a health setting, they run the risk of infecting others as they move from patient to patient. If they’re sidelined with an infection, they aren’t easily replaced, adding more strain on the health system as the number of caregivers declines. So it’s crucial to catch any infection in their ranks early, which may mean testing as frequently as every day.
Other workers in essential, high-exposure roles like grocery store clerks, aides in assisted care facilities, and delivery personnel should also be tested regularly.
Mitchell said another high priority should be testing people in situations where Covid-19 infections can run rampant. “Nursing homes, senior living facilities, prisons, immigrants in these big camps who are in very, very close quarters,” Mitchell said.
Another important category is people who could benefit from early detection and treatment, particularly those with preexisting health conditions, like high blood pressure or compromised immune systems.
Mitchell added that testing should not just center on diagnosing patients, but some resources should also be used to estimate the prevalence of the virus in the population. This information can be valuable for public health officials, providing population-level data that can help them interpret individual tests. Data can be gathered with diagnostic tests as well as serological tests for antibodies to the virus, which can identify people who were previously infected but don’t have an active infection. That protocol could mix random tests with contact traces.
“That’s easily justified under a ‘greater good’ rationale,” Mitchell said. “That would allow us to take a look overall at the country in a way that has some scientific support for choosing where to lighten up on physical distancing or being at home all the time.”
But as long as testing capacity is limited, there will be people who want tests who can’t get them. Without a massive scale-up in testing capacity, more difficult decisions about allocating tests lie ahead.