The West Virginia National Guard assists with storing samples at a school testing site. (Senior Master Sgt. Emily Beightol-Deyerle/U.S. Air National Guard/)
When it comes to COVID-19 testing, we’ve come a long way since the beginning of the pandemic, when people were lining up in their cars to get swabs stuck deep up their noses. There’s a more diverse array of tests out now, including rapid saliva tests and tests that can be completed entirely at home. But many parts of the country are still facing a shortage of supplies. Meanwhile, wait times for results are stretching for weeks, forcing lab technicians to work around the clock. In some cases, the results are also flat-out wrong.
Here’s a snapshot of what COVID-19 testing looks like across the country right now.
What do the tests show so far?
The seven-day average for positive COVID-19 tests is close to 11 percent in the US, according to data from the COVID Tracking Project. As a rule of thumb, the World Health Organization considers a positivity rate above 5 percent too high for governments to reopen.
Daily rates of new cases are high but lowering in 10 states, according to the New York Times case tracker. Many of those states posted the worst COVID-19 rates in the country over the past few weeks, such as North Dakota, South Dakota, Iowa, and Wyoming. New cases are high and staying high in 39 states, and the mid-Atlantic and Northeast are being slammed especially hard.
Because the Trump administration hasn’t been keeping a steady national count of daily testing, the data is broken up by states and localities, which makes it harder to keep consistent and compile. Most reports this far have relied on independent research projects run by universities, but that only gives us a glancing look of what’s happening in different regions. There’s no way to know which places aren’t getting their fair share of tests.
There’s also an inconsistency in getting results in different areas of the country, which further sets back the data. Currently, wait times range from a few hours, to four or five days, to even weeks. “When you add the delays, it makes the test a little bit useless,” says Gigi Gronvall, an immunologist and senior scholar at the Johns Hopkins Center for Health Security. “People might think that they’re okay, but in fact they’ve been spreading the disease for days and days.”
What kind of COVID-19 tests are available now?
At the beginning of the pandemic, people with coronavirus symptoms had to resort to antibody tests to try to figure out if they were infected, Gronvall says. But antibody tests, also known as serology tests, aren’t intended for COVID-19 diagnosis. “That was complicated by the fact that a lot of the serology tests were junk,” Gronvall adds. Although accuracy increases in the weeks after infection, many of the early antibody tests were inconsistent and unreliable. One preprint study that has not yet been peer-reviewed used12 antibody tests on pre-pandemic blood samples and found that 0 to 16 percent came back positive for COVID-19.
Now, there are a wider, more effective variety of options for diagnostic testing. The gold standard, says Omai Garner, the director of clinical microbiology in the UCLA Health System, is the PCR test, which replicates and senses viral RNA in samples. While most PCR tests are conducted by health care professionals, people can also take saliva samples and and swab their nostrils at home. “They all have pretty good accuracy in the symptomatic patient,” Garner says. Asymptomatic individuals should still get tested by a professional.
Another advancement in testing is rapid tests. Although some run on PCR, many are antigen tests, which detect specific coronavirus proteins. The antigen method is less sensitive and may give false negatives that should be re-confirmed. Despite these caveats, they do have benefits as people return to their day-to-days. “Antigen tests align better with human nature because you get an intermediate result,” Gronvall says. “Then you can act on it immediately.”
How does testing still need to be improved?
While it’s hard to judge how many COVID-10 tests need to be conducted daily, it’s clear that the US is underperforming compared to other countries. The Rockefeller Foundation, a private foundation dedicated to science and philanthropy, estimates that we need to run about 30 million tests per week to curb the spread of the virus. But the US is doing just a fraction of that. On December 7, for example, the COVID Tracking Project reported a daily total of 1.8 million new tests.
Accuracy also continues to be an issue for some tests. The companies behind the most popular PCR tests say that they have 100 percent sensitivity (positive rate) and specificity (negative rate). For the most popular antigen tests, sensitivity ranges from 84 to 97.6 percent and specificity from 96.6 to 100 percent. However, those numbers come from studies conducted in strictly controlled lab conditions. In practice, accuracy is likely to be lower.
Results vary, too, because people often use tests incorrectly. For instance, asymptomatic individuals shouldn’t take antigen tests. Emerging data shows that accuracy rates might be as low as 30 to 50 percent in this group because the method is less sensitive to trace amounts of the virus.
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