- Learn the difference between different types of tests
August 6, 2020 / Infectious Disease, Health Essentials from Cleveland Clinic
With the coronavirus (COVID-19) pandemic continuing to surge globally, there are new questions about testing, including what kind of tests are available and whether or not you should get one.
Effective testing is essential in helping slow the spread of the virus by identifying those who have the virus and enabling treatment or isolation. Testing is also crucial to learn more about how the virus spreads and how prevalent it remains in a given community.
In the United States, however, those efforts have, at times, been hampered by a shortage of materials for testing, leading the Centers for Disease Control (CDC) to publish guidance for local and state health departments as to which populations should be tested for coronavirus.
With cases still climbing throughout the summer, we caught up with pathologist Brian Rubin, MD, PhD, to talk about the difference between certain tests and if you should get a test even if you’re asymptomatic.
Rapid response versus longer response tests
The emergence of rapid response tests has enabled quicker turnaround for results, a big advantage in making sure patients who test positive are able to quarantine and curb spread of the virus in a more timely manner.
Response times for tests used at Cleveland Clinic have a wide range but all are turned around within 24 hours, according to Dr. Rubin. “The most rapid turnaround times have a maximum of six hours, with a median turnaround time of two to three hours,” he says. Additional tests used have turnaround times of within 10 hours and within 24 hours. also fine.
The turnaround time, he says, depends on the diagnostic platform used for each test and whether they’re automated or not. One manual test has a median turnaround time of 14 hours and a maximum of 24 hours. “It takes more time because we physically have human beings doing all the work,” Dr. Rubin says.
Automated tests are quicker, he says, because you’re able to put a swab into a test cassette, the casing that holds the sample, and put the sample into a testing device that’s able to perform the test rapidly.
“The problem with rapid testing is that you can’t do a lot of it at once,” Dr. Rubins says. “The throughput is very small. With manual tests, while they take longer, you can scale up and do tremendous numbers of tests.”
Saliva-based tests versus nasal swab tests
If you’re tested for coronavirus by a medical professional, it’s most likely going to be a nasal swab. But, throughout the pandemic, the FDA has approved both at-home nasal swab and saliva collecting kits for testing.
We previously talked to pathologist Gary Procop, MD, about the usefulness of these at-home kits. According to Dr. Procop, the accuracy of the at-home kits rests on the ability to obtain a good sample without the presence of a healthcare professional to advise the collection. Given the risk of a pooer sample collection and the cost of the kits, as much as $100, Dr. Procop advised that, as long as you’re asymptomatic, it’s best to hold off on using one.
But the use of saliva samples does bring up the question of whether saliva offers as accurate a result as nasal swabs. Dr. Rubin says, “We’ve studied saliva and though we never validated it, in our studies, we found that its ability to predict whether somebody was COVID positive was the same as a nasal swab.”
The issue, he says, is “there’s an indication that it might be slightly less sensitive” than a nasal swab test. “But,” he adds, “the sensitivity difference is marginal enough that in our study, it didn’t reveal any differences in overall ability to determine positive versus negative.”
Should you get a test if you’re asymptomatic?
In a word: no.
In its guidance, the CDC suggests testing for a narrower range of the population than the general public, namely for those who are showing symptoms of COVID-19, members of vulnerable populations have been exposed to the virus or those who have previously tested positive to see if the virus has run its course.
Additionally, Dr. Rubin adds that an asymptomatic person should only be tested if they’re due to have a procedure in a hospital or doctor’s office setting. “Asymptomatic people should only be tested in the pre-procedural or pre-operation period. People who are at home, not coming into the hospital for a procedure and are asymptomatic don’t need testing.”
If you come into contact with someone who tests positive or you think you may have otherwise been exposed to the coronavirus but remain asymptomatic, doctors recommend that you self-quarantine for 14 days. If you develop symptoms during that time, contact your healthcare provider for next steps, including a possible test.