Cases of COVID-19 are at an all-time high, putting tests in high demand and leading the Delaware Division of Public Health to say that anyone who is sick should assume it’s a case of the coronavirus and stay home except to test.
The division is also urging Delawareans to refrain from visiting emergency rooms for tests and to look for appointments instead.
There are a slew of options: nasal or saliva, results in three to five days or in as little as 15 minutes. And if there are no appointments available, many must resort to store-bought rapid tests.
But what’s the difference?
The Delaware State News consulted Gregory Hovan, biosafety officer and quality coordinator at the DPH laboratory, to set the record straight on testing. He is responsible for safety and quality within the lab and explains the various kinds of tests, what they do and how to choose which one is right for you.
Q: What are the different kinds of tests available?
A: There’s the antigen test, which is fairly simple. You can use them anywhere with little to no education behind it, so they can be used in a lot of different settings, like in a school or at home, any remote setting. The rapid antigen tests are what they typically have at the store, which you can take home to self-test and get results in five to 15 minutes. They look for the SARS-CoV-2 proteins and indicate whether you are infectious or not. Then, there is the PCR test, which is much more sensitive than antigen tests and uses a technique called NAAT (nucleic acid amplification tests) to determine if a person is currently infected with COVID-19. The PCR looks for the genetic material of SARS-CoV-2 and can provide a different window into what identifies as a positive COVID case. Now, if you’re looking to identify variants, you have to look at the entire genetic code, which is where DNA sequencing comes in, which is a very complex test.
Q: If the PCR test is more “sensitive,” does that mean it is more accurate and reliable?
A: Not at all. Rapid tests are very reliable when they are used in the appropriate setting. These methods have been approved for folks based on where they’re located, what kind of symptoms they may have or what that onset may be. They don’t detect the genetic material but detect the presence of the virus and whether or not you are contagious.
Q: What is the difference between tests that use nasal swabs and tests that use saliva or mouth swabs?
A: Antigen tests can be performed on deep-nasal (nasopharyngeal) or anterior-nasal specimens, and NAATs can be performed on upper-respiratory specimens, basically any type of nasal swab or saliva. But it all depends on who developed the test, and the (Food and Drug Administration) scrutinizes these tests thoroughly. Early on in the pandemic, researchers weren’t sure how to identify SARS-CoV-2, but most common respiratory viruses you find far up into your nose, almost towards your throat. But science has progressed so we don’t have to do those deep nasal swabs anymore. Further research determined that you can pick up the virus right inside of your nose. Sometimes, saliva might not be as specific or sensitive. It depends on the person and on how much virus is in the mouth, so there’s only a couple of tests out there that might be approved for saliva. You also have to follow the directions on every test to ensure you’re getting an accurate result.
Q: When is it necessary to take a COVID-19 test?
A: If you think you are sick, get tested. The idea is to stop the spread of any infectious disease. So if you think you’ve been exposed, if you think that you’re sick, get a test and confirm it.
Q: How do I decide the type of test I need to take?
A: So when you’re doing something that’s a high volume, like a congregate setting, something like school or a long-term care facility, having those rapid tests where you can get results in as little as ... five to 15 minutes, it works out very well where you can quarantine individuals and stop the spread. You would need a PCR test when you need a confirmatory test. (For) somebody that could possibly be part of an outbreak but is presymptomatic, or they were exposed and wanted to be sure they didn’t have something, or if they were doing something at a certain time like going on a flight, having that PCR, you can make sure that there’s no genetic material. They are looking for RNA (and) DNA, which is more abundant than a protein, which the antigen tests are detecting, so (that genetic material) would be picked up before symptom onset and also when you are past infectiousness and just have residual RNA or DNA floating around in your system.
Q: So I’ve gone to a DPH testing event and done my swab. I seal the bag and drop it in the collection bin. Where does it go from there? And how does the process work once it gets to the lab?
A: We have a courier for each county, and we also work with our National Guard, who provide couriers to drive to pick up samples. Then, we can have samples back at our facility the same day that they are collected. Once they get back to our facility, it goes through this really robust, comprehensive testing process. The first thing is all the paperwork or labels that come with the swabs are checked to make sure they are labeled with the appropriate name and personal information and entered into our computer system, so everything is tracked. Then, we take a portion of that transport media or liquid in the sample and isolate it from the virus, with a chemical that inactivates the virus. That reduces the infectiousness and risk to exposure to our laboratories. Samples are then sent to the PCR lab, where the inactivated sample is sent through a filtration process, where it removes all the cheek cells, the boogers, the liquid, all that junk that’s in there except for the genetic material. So all you’re left with is pure genetic RNA. Now, the PCR system that tests the RNA is very sensitive, and it can measure even a tiny amount of RNA in a sample, which takes about four to six hours.
Q: How often might people be getting false negatives or false positives? Is this because they’re not paying enough attention to the test directions?
A: Overall, it is not very common. Sometimes, it is hard to track that information because someone takes a home test, and they may not report the results to somebody, or they might go to a clinic or a pharmacy to get a test. And by the time those test results are taken into account, it’s very difficult to ascertain whether that person was negative on their test but was actually positive. I know that we at the state laboratory scrutinize our testing very highly, so we’ve gone through a lot of what we call quality-control measures. Not that other folks aren’t doing that, but sometimes, it can be lost in the shuffle when you’re doing a drive-thru or something like that. Depending on who is swabbing who in the car and if it’s not observed, there’s a lot of different things that you could miss in the process.
Q: If people take an at-home test and get a positive result, should they report it?
A: It would really help DPH to track that type of information. So ... they can call the number 211 or email firstname.lastname@example.org to talk to some of our wonderful epidemiologists or contact tracers. It helps us keep track of who is where, and it prevents other exposures from occurring because they can keep those numbers in check and see where they are at the county level. It helps us provide information to the public and keep them informed.