Coronavirus in Context: Saliva Tests For Coronavirus: Are They Useful?

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You're watching Coronavirus in Context. I'm Dr. John Whyte, chief medical officer at WebMD. Today, we're going to spend a few minutes talking about a new test for coronavirus. It's a saliva test. And I'm joined by Dr. Andrew Brooks. He is professor of genetics at Rutgers. Dr. Brooks, thanks for joining me.

My pleasure.

Let's start and explain to our audience. How does this test work?

So the collection of the sample is different than what we've traditionally heard about and what we started with in the beginning of molecular testing for coronavirus. The use of saliva, um, makes collection more robust, more simple. You spit into a tube, up to a line that's on the tube. You screw the cap on, which has a preservation agent, which drops down into the saliva and preserves it.

When the sample gets to the lab, the test is really no different than what we've been doing for swabbed-based analyses, where we extract nucleic acid. We do qPCR to look for the presence of viral genes in the sample.

So you're using the same technology as they used on the swab, in terms of PCR. Is that right?

Similar to-- a very similar detection technology and molecular process. What's different is the biomaterial and how we collect it.

Mm-hmm. And the collection, though, is similar for our viewers, as they might do for some of the, um, in-home DNA kits. Is that right, in terms of spitting?

In fact, it's-- it's very similar to the point when we started at the first drive-through in New Jersey. And I was there. A few of the people that were coming up to be tested were handed the device. And they said, no, I already know where I come from. I've done ancestry.com. I'm here because I think I'm sick. All right, so, um, it is-- it is very much similar in the process of collection, yes.

And this is not antibody testing. This is a diagnostic test for coronavirus, COVID-19. Correct?

C-- correct.

And we've been talking a lot over the last few weeks about sensitivity and specificity, positive predictive value, negative predictive value, recognizing we're not trying to give a biostatistics lesson to our audience. But can you help explain and to talk a little bit about the accuracy of this type of test?

So the accuracy of-- of qPCR and molecular detection is very high. At the outset, you want to make sure that the design of the probes and primers that you're using are specific to what you want to detect, so you know that the specificity is for the virus or the transcript or whatever you're looking for.

And-- and all of the tests out there have a very high level of specificity. It's-- it's not like an antibody test, where there may be cross reactivity to proteins and similar organisms. So the specificity is-- is-- is direct.

The specificity, if it's very high, it's also going to allow us to rule in a disease, if it's positive. Correct?

Correct. Um, but also to keep in mind, that all of the emergency use authorizations are for presumptive diagnoses. Um, and all negative tests from any sample source should be tested from a different sample source when clinically indicated. And that's part of every emergency use authorization.

Good point.

So it's really important-- it's really important that people know that, if they're symptomatic and they're COVID-19 by any molecular test, including saliva, and their symptoms increase and under the care of the physician, or change, that needs to be confirmed. Because it's not a true confirmatory results. And the same thing with positive, it's a presumptive diagnostic.

You know, we're in very different times right now with the FDA and these emergency use authorizations. So people really need to understand the process.

And you were going to talk about it's sensitivity. So it's highly specific how sensitive it is.

Right. So-- so s-- sensitivity takes into consideration a number of things with respect to COVID molecular testing, in my opinion. Sensitivity is determined by the number of copies you can detect per amount of material that you have it in.

And-- and all of the FDA authorizations are based on determining the level of detection, the upper and the lower level of detection. And that's done by spiking in viral transcripts into the matrix that you're testing-- in this instance, saliva-- carrying it through the process, and seeing what you can detect. So really, understanding whether or not the saliva matrix is different than the universal transfer media or the viral transfer media presence is what gets at the absolute sensitivity of the test.

Our sensitivity is approved for down to 200 copies of the viral transcript in one mL of-- of media.

Mm-hmm.

Now, h-- how does that translate into false negatives and performance--

Mm-hmm.

--um, uh, you know, for patients? Uh, that's a little bit different. Because what that number doesn't take into consideration is the variability associated with sample collection. So whether you're self swabbing [INAUDIBLE] or-- or you're going for a very uncomfortable nasopharyngeal swab or just spitting into a tube, there could be different impacts on the robustness of collection, which really translate into false negatives and could negatively impact that-- that sensitivity measure we were just talking about.

Is the test currently available?

The test is currently available, yes.

And where would, uh, people go to-- to get that test?

So, um, primarily, if you go through your healthcare providers--

Mm-hmm.

--you can identify what tests they are offering and where they get them from. So we have partnerships, um, with, uh, different health care providers. And most of those are for, uh, physician-ordered, physician-guided, um, a collection or a supervised collection.

OK.

If-- if you're looking for a home collection, which we were approved a week ago from the FDA, then you need to, uh, find a telehealth partner that-- that provides those tests.

OK.

Because it's important to point out that at-home collection does not imply home testing. It does not imply self-testing.

OK.

It's important to point out that the test still has to be ordered by licensed physician in your state. There still has to be the proper identification of the right person in the right test--

Mm-hmm. --or device that you're using. And the test, then, needs to follow all the EUA authorizations. So, um, there are three partners, uh, currently, uh, supporting our test. Uh, there's Vault Health, um, Vitagene or IO Health and ixlayer.

Um, we have vetted and approved their process to ensure that home collection is being done the way the EUA authorizes.

And test results come back in about 48 hours. Is that correct?

Once they get the lab, our turnaround time is approximately 48 hours. Um, it can be as soon as 24. It can be as late as-- as 72, if a retest is required. But, uh, 48's a pretty reliable number.

Well, this is one more tool in our tool box, uh, for testing. Is it going to change the testing paradigm?

I think what it does is it makes testing more available. Um, there are no tests currently approved for, um, truly asymptomatic, uh, individuals. Uh, we're collaborating with the FDA and with others to-- to try and get to that point. Um, and-- and once the FDA is comfortable with respect to the incidents or understanding the incidents and how that impacts sensitivity, then saliva will really change the landscape quite a bit. You know?

For the immediate past, it's been about getting patients to the test. Now, we can get the test to the patient, which will drastically impact the number of tests that can be done, a larger screening, um, as well as being able to help not just patients that are sick. But, ultimately, once asymptomatic testing is more commonplace, uh, companies and other organizations allowing to screen and protect employees and people that are participating in everyday events, um, so that we can get back to what we remember our world being.

Well, Dr. Brooks, I want to thank you for taking the time to speak with us today.

My pleasure. And I want to thank you for watching Coronavirus in Context. I'm Dr. John Whyte.

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