March
25, 2021
Weighing the pros and cons of new tests
Since the COVID-19 pandemic spread across the globe, science has
made great strides, from the rollout of multiple vaccines to the ability for
people to now test themselves for the virus at home.
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Adding to that latest accomplishment are the recent emergency
use authorizations (EUA) handed out by the U.S. Food and Drug Administration
(FDA) for a new group of at-home COVID-19 tests that allow users to get results
in 30 minutes or less.
To get a better idea of what you can expect from them, we talked
to infectious disease testing expert Gary W. Procop, MD.
Understanding the new round of at-home tests
Dr. Procop and his colleagues reviewed three of the available
at-home tests, two of which are only cleared for symptomatic individuals and
require a prescription. The third is available over-the-counter (so it
doesn’t require a prescription) and is cleared for use by both symptomatic and
asymptomatic people.
These tests are essentially home versions of rapid test kits.
You collect your own samples and get the results at home. There’s no sending a
swab to a lab and waiting days for a result.
These types of at-home tests also make it possible for you to
find out if you’re positive for the virus without having to visit a healthcare
provider’s office, possibly exposing others.
In most cases, you can get the test from your healthcare
provider and you’ll have the option of having them administer the test or
taking the test home. These are approved for at-home use by adults, with
applications for children varying for the different tests. Once the results are
in, the reporting of the results to local health officials also varies by
manufacturer, so read the instructions carefully.
But just as with the self-collecting at-home
specimen kits, you should have an understanding of how each test
works and the pros and cons of the tests.
Isothermal amplification testing
The Lucira COVID-19 All-In-One
Test Kit, uses a process called isothermal amplification. It’s a
similar process to the polymerase chain
reaction (PCR) lab tests that are considered the “gold
standard” for COVID-19 testing.
Like the PCR test, an isothermal amplification test makes copies
of the genetic material from your self-collected swab, including any viral RNA
that may be included, in a process called amplification. By making all these
copies, it’s easier for the test to detect any presence of the COVID-19
virus.
There are two big differences between the home version and the
laboratory version of this test. First, the laboratory version pulls out that
genetic material, including any genetic material of the virus, from the rest of
the specimen. Second, while the laboratory version uses heat in the
amplification process, the home version uses enzymes for amplification or
antigen detection methods.
By removing the genetic extraction and heat from the testing
process, Dr. Procop says, this type of testing becomes more doable at home and
doesn’t require the more complicated laboratory equipment that’s typically used
for laboratory-issued PCR tests.
Antigen testing
Two of the at-home tests — one produced by Ellume and the other
by Abbott — are antigen detection tests. These tests look for antigens,
proteins produced by the virus that prompt a response by the body’s immune
system. “It’s the same process used to test for strep throat,” Dr. Procop
notes.
Of the two antigen tests, the Ellume test does not require a
prescription and has been cleared for use by both symptomatic and asymptomatic
individuals. Anyone from the age of two and up can have the test
performed, with the test for children being performed by an adult. The test
even has its own smartphone app that provides a walk-through on how to collect
a specimen with the included swab.
Once collected, the device tests the specimen and delivers
results in about 15 minutes to the app by way of a bluetooth connection. One
thing to keep in mind: While you have the option of whether or not to share the
results with your healthcare provider, the Ellume system does send positive
results, along with your age and zip code, to local health officials for the
purposes of tracking case rates in your area.
The Abbott test, alternately, requires you to undergo an online
screening via the eMed website. If your symptoms meet the necessary
requirements, you’ll be shipped a test overnight.
Once the kit arrives, you can log onto the platform and receive
a live video walk-through of collection via nasal swab by a guide. This test
also comes with its own app that allows you to access test results, which are
delivered within 20 minutes. Like the Ellume test, positive results are
reported to local health officials for monitoring the spread of the virus.
The pros and cons of at-home tests
There’s a lot to like about these at-home tests. Besides the
previously mentioned advantage of keeping potentially infected patients home,
there are other positives. They’re relatively affordable, with a price range of
$24 to $50. And they should also be relatively easy to obtain, even if a
prescription is required.
But you should still keep certain potential drawbacks in mind
when thinking about using one of these tests.
Collecting the sample
“One of the issues with these tests can be the quality of the
specimen collected by the patient,” Dr. Procop says. “The collection is left to
a user who has less experience than a healthcare provider and an
incorrectly-collected sample can lead to an incorrect test result.”
While the idea of wiping a swab around the inside of your nose
seems simple enough, there are plenty of ways for things to go wrong. It’s very
important, Dr. Procop says, for anyone using these tests to follow the included
instructions. “The collection is safe to perform yourself,” he says, “it’s just
essential that it’s done correctly.”
Test accuracy
Overall, the three tests perform quite well with accuracy
ratings above 90%. But each has some issues to be aware of.
With the Lucira test, the removal of the genetic extraction step
makes the test more convenient for at-home use. The downside, Procop says, is that
the genetic material being copied for virus detection by the at-home version
isn’t quite as “clean” as with the laboratory version of the test.
“Without the genetic extraction, the specimen contains cellular
debris and other biological material that can interfere with the amplification
part of the test,” he says.
As for the Ellume and Abbott tests, they are (like healthcare
provider-performed rapid antigen tests) slightly less accurate than PCR tests.
“These rapid tests have a tendency to generate some
false-positive results in asymptomatic people,” Dr. Procop notes. “So if a
person is asymptomatic but has been exposed to someone else who has COVID-19,
it can create some confusion as to whether it’s a false-positive or an
accurately positive test.”
In that case, he says, additional testing would be needed.
The bottom line: A big step forward, but keep
practicing guidelines
These tests and their availability via the FDA’s emergency use
authorizations represent a big step forward for COVID-19 testing and prevention.
“This means there are now more tests available and there’s a better chance
someone who’s infected can more easily isolate thanks to these quick results,”
Dr. Procop says.
But, even so, it’s important that everyone continues to follow
current CDC guidelines, he says. “Taking precautions – maintaining social
distance, frequently washing hands and wearing a mask – are still essential to
preventing the spread of COVID-19.”
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