The COVID Testing Catch-22
The Key to Managing the Pandemic, and Why We‘ll Never Do It Perfectly
Everybody agrees the only way to manage the SARS-CoV-2 pandemic is to know how bad it is by conducting tests, and lots of them, right? Well of course. How else?
But there’s a problem. And there doesn’t seem to be a good solution.
First, Some Background
There are three types of diagnostic tests (well, really two, one is more of a “yes, you had it”)… They are:
- PCR-based testing. This is a fairly complex type of laboratory testing that multiplies minute amounts of suspected viral genetic material until there’s enough to actually tell whether it really is the coronavirus. These tests are often referred to as the “gold standard” and have a pretty good degree of accuracy (around 95%+, give or take). The problem is that transporting samples to a lab, extracting DNA/RNA materials, processing the results, and reporting back can take days or even weeks. Making things worse, labs are seeing higher throughput than they’ve ever known and they are often overwhelmed. By the time you get your result, you’re probably already being treated, recovering, or dead. But at least you have the satisfaction of knowing they feed the daily statistics.
- Antigen testing. This type of testing looks for the presence of particular proteins that are peculiar to this virus, thus indicating its presence. Recently-developed antigen-based test kits are as fast and simple as pregnancy tests — they require only a bit of saliva or a nostril swab and can give a result in minutes. The latest kits seem to be on a par with the accuracy of PCR tests — given the right conditions (more on that later).
- Antibody (serology) testing. This type of testing looks for your body’s immune response to the virus. It requires taking a blood sample, which is why it’s also called a serology test. Antibody tests basically say “yes, you had it at some point” or “nope, you haven’t had it yet”. Rather than diagnosing individuals, antibody tests are more useful for getting a handle on how many people are actually contracting the virus, whether they’ve displayed symptoms or not. They also can play a role in figuring out just where the hotspots of spreading are occurring. In addition, these tests help screen plasma donations to treat severe COVID-19 cases. Antibodies your body creates to fight the disease can help another person fight it.
SO… Here’s How We Beat This (Right?)
OK, so back to the plan. Testing, testing, and more testing, right? Athletes get tested daily (because they are more important than the rest of us, apparently). As soon as they test positive, they go into quarantine so their teammates can still make millions for the team and keep us from going out of our skulls while we languish in lockdown.
Other businesses and organizations need to do the same. That’s the only way to really get a handle on things and start returning to something like a reasonably functional economy. And with the advent of these quick, cheap antigen tests, it starts to become feasible for local restaurants and shops to test their staff regularly. The same goes for schools, jails/prisons, clubs, local government agencies, and every other kind of organization you can name. Hooray! Great news, right?
The Catch (22)
Now here’s the catch, and the reason why we’re unlikely to ever have a perfect screening system: both of the actual diagnostic tests (PCR and antigen) require detectable levels of the virus. In fact, you’re probably going to test negative until/unless you have enough viral load to have symptoms. So what is the point of even testing anyone who isn’t showing symptoms?
A study that examined false-negative rates post-exposure, found that during the four days of infection prior to symptom onset, the probability of a false negative on the PCR test went from 100 percent on Day 1 to 67 percent on Day 4. And even on the day individuals began showing symptoms, the false-negative rate was still 38 percent, dropping to 20 percent three days after symptom onset.
In other words, even the “gold standard” test wasn’t much use unless administered at least three days after symptoms occurred. This is the “dirty secret” that for some reason we don’t hear about. And remember, you probably won’t even know that result for several days after the specimen was taken.
Now let’s add in another nice nugget of info:
A recent report from the Centers for Disease Control and Prevention (CDC) estimated that 40 percent of all coronavirus transmissions happen from people who show no symptoms. That’s either because they’re asymptomatic or because they’re pre-symptomatic (meaning their symptoms have not yet surfaced).
Nice, right? Let’s recap: the best test for diagnosing COVID-19 isn’t reliable until you’ve already displayed symptoms for three days, but almost half of all spreading occurs before symptoms display.
Accurate results for both PCR-based (NAAT) virus testing and antibody (serology) testing depend on the point when samples are taken during the clinical progression of COVID-19 — and perhaps other viral diseases.
That has to put a serious hitch in any testing program.
Now for the Good News
There is one saving grace that makes having a screening program in place viable. As bad as the tests are at detecting the virus — or more correctly, at detecting it in a useful time frame and stage of the disease — they excel at producing valid positive results. In fact, both PCR and antigen tests have a nearly 100% accuracy rate for positive results. In other words, if you get a positive result, you almost certainly have COVID-19.
What It Means for Testing Programs
So it’s clear that it’s impossible to create a perfect testing program. The tests themselves aren’t perfect, timing matters. And let’s not forget human error — often the biggest contributor to inaccuracy.
But it’s also clear that there is no alternative. Our best hope for getting a grip on the pandemic and navigating to the normalization of activities is testing programs. So here’s the takeaway:
- Establish regular — preferably daily — testing for your staff/members/residents/students.
- Use the new rapid antigen tests to screen, so you get results right away.
- Quarantine anyone who tests positive.
- Don’t trust negative results. Maintain CDC-advised precautions (masks, social distancing, hand-washing, sanitization).
- Follow up any positive results with repeated PCR tests until there are no symptoms and the patient tests negative twice in succession.
- Preferably implement a professional data management solution to ensure all testing and patient data are handled (a) in a secure, HIPAA-compliant fashion and (b) with sufficient automation to minimize or eliminate errors.
Test often and effectively. It’s not perfect, but if we do it right, it will be good enough. And together, let’s beat this.
To learn more contact LabLynx at sales@lablynx.com, 866-LABLYNX (522–5969), or LabLynx.com.
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