Transcription:
COVID-19 and Testing

Host: So did you know, there are two types of COVID 19 tests. We're going to learn about each of those. And we're going to talk about the challenges of testing and why a negative COVID-19 test is not a green light just to resume all normal activities. And go unmasked.

So let's learn more with Dr. Christopher chow, a physician at wake med, urgent care. He also served on the urgent care association and the college of urgent care medicine. COVID task force last summer.

This is wake med voices, a podcast from wake med, health and hospitals. I'm bill clamp Roth. Dr. Chow. Thank you so much for your time. It is great to talk to you. So actually there are two types of COVID 19 tests. There's the molecular test and the antigen test. Can you tell us more about these two tests and what is most important to know about each?

Dr. Christopher Chao: I appreciate you having me on this podcast. I hope that the information that we've delivered today, we’ll be valuable to our listeners. there are two different types of testing. And when we talk about the two types of testing, a molecule or antigen test, we are actually referring to testing that is booking for the presence of the virus.

For background COVID-19 is the disease. COVID-19 is caused by the SARS cov two virus. when you read articles and look on the internet, you may see references to a SARS Coby to past. That is effectively the same as a COVID test.

The molecular test. Is a technique where we are booking for presence or evidence of the genetic material of the SARS cov two virus. Examples of molecular testing. Are tests that are sent to a reference laboratory such as lab, Corp or quest. Tests that are done at a facility point of care tests at a hospital or laboratory.

Examples are homogenic Panther or BD max. Or it can be done. As a portable test. And the two that are currently most common in the market. Our Abbott ID now. And Seth, you had Expedia antigen test is slightly different from a molecular test in that it's not looking for the genetic markers of the SARS cov two virus.

It's looking for the capsular protein that the virus produces.

The caveat with the antigen test is that it is generally not as accurate as the molecular test. However in certain clinical situations. The antigen test can be as accurate as a molecular test. Mainly if the test is performed in a symptomatic patient. Within five days of the onset of symptoms. The reason it is important to understand. There are two types of tests.

Is because. There are patients that are coming into the clinic asking for travel documentation. And it is important to know that. The antigen test may not be acceptable as a valid test for travel purposes.

Host: Okay, so that is a good distinction. So if somebody is traveling out of the country and a test is required, the antigen test, which is the more rapid of the two tests may not be accepted where the molecular test, as you said, that is where it gets sent to a lab. That one generally has a higher degree of accuracy. Is that correct?

Dr. Christopher Chao: Correct. However, a molecular test can also be a rapid test is I think that's what confuses patients. if someone were to go through a drive through testing and that passed the central reference lab, it is most likely going to be a molecular test. Whereas, if you go to a clinic like an urgent care clinic,

Or if you go to a primary care clinic and they do the test white, um, fight. It could be either a molecular test or antigen test.

Host: Okay, so that is really good to know. So let me ask you this from a physician's point of view. Why is COVID-19 screening such a clinical challenge?

Dr. Christopher Chao: It's a challenge because some patients who are infected with. As far as Coby two or COVID. Don't ever show symptoms. There are other patients. Who are contagious. Inner capable of transmitting the virus to others. For several days. Before they show symptoms. the challenge is if someone comes in.

And they are having symptoms. And they come in for testing and the test is positive. They may have been spreading that virus around. For the past two days. Without even knowing it. The second group of patients that were so worried about. Are patients who have very mild disease. Or asymptomatic.

But are actively infected with the virus. It is capable of transmitting Illness to others Who don't even know that they need to be tested.

Host: Right. So the asymptomatic carriers to me. It seems like that is really what is scary about this and the new guidelines to not gather with your family and friends, cause you feel like, Hey, I know them. they wear masks all the time and they're healthy and they're okay. So we can get together and we're going to be in the same house for a couple of hours and there's no open windows and the masks are off. And, but that person might have been in the grocery store two days before.

Picked it up on knowingly. And now feels fine because they're asymptomatic and is spreading it to mom and dad and brother and sister. Right? That's the crux of the problem here.

Dr. Christopher Chao: hit it right on the nail, that is the problem. The testing. Represents a point of time. just because you're negative at the time of the test, does that mean that you are already infected and are going to show symptoms two days later or beyond? The asymptomatic phase or if, someone becomes infected with COVID.

They may not show symptoms for up to 14 days after the exposure.

if they're infected on day one, and they go. To if gathering. To visit family. Or to go to a party on day five. They may already be shedding virus and capable of spreading it to others. But they may not show signs or symptoms until they fix for day seven.

What's even more problematic is let’s suppose you're exposed on day one. You can test yourself on day two. And be negative. You can test yourself on day four and be negative. You can test yourself on day six and be negative. It's an on day eight. You show signs of fines of illness. But at that point, you've already been spreading it around.

Host: Wow. All right. So it's easy to see why this is such a challenge right now. So if I drive to a high-risk state and when I get back, I'm supposed to quarantine for two weeks, but I don't want to quarantine for two weeks. When I get back, I'm just going to go get the test to see if I'm negative. So what you're saying is if I go and get that test too soon,

It may come back negative, even though I might still have COVID 19. So that's why this is such a challenge. Depending on the timing of when you get the test. Is that right?

Dr. Christopher Chao: Correct. the way that the test is. Designed if the test is positive. It's pretty much guaranteed that it's a positive. It's the negative tests that are problematic, particularly if someone was asymptomatic. The test can only detect what it can detect. And if the viral load early infection and well, I mean by viral load is how much virus is in your respiratory tract.

is low in the beginning of the infection. It's quite possible that the test just isn't. Technically able to pick up that virus. And so what we've been begging patients and what we've been trying to convey. Is that. If you get a negative test, like you said, it's not a green light to go back to business as normal.

If you get a negative past. You still have to wear a mask. You still have to follow social distancing guidelines. Because. There is a possibility that that test is a false negative, is that you are infected or harboring the virus. We can't detect it. Is there a day or two later? You show symptoms or you're giving the illness to someone else. So I could love them one or a family member.

Host: This is really good information and it really helps to talk this through to clarify it because I think a lot of people have that misunderstanding of, Hey, I went and got tested. I'm negative. I'm coming home for Christmas. I'm good. So the negative test really is the one where you're up in the air. The only thing we know is when somebody tests positive. Okay. You've got it.

Well, there can be a false positive too, but generally if you test positive, you have it, the negative, depending on, like you said, it's only a point in time. The negative is what's so challenging about this.

Dr. Christopher Chao: Yes. And the positive test is still useful from an epidemiological and from an infection control standpoint. Because once we identify Soma who is positive. We know that that is known risk. Right. Whereas if I'm a kind of negative. That doesn't mean that you have the green light. The other question is we get a lot of calls from patients who call and say, well, I was exposed.

And I want to test. The question is when is the optimum time to get that test? Is it the day after exposure is at five days after exposure that seven days after exposure? And so if you test too early, you could also get a false negative. That's not a fault of the test. That's just the fault of the virus and fault.

How this infection progressive. when someone comes in and they say, yeah, I was at a party on Saturday and I'm asymptomatic. And I want to test and it's Tuesday. It's probably too early. And even if that person was infected and capable of transmitting illness, that test really cannot pick that up at that time.

Ideally, there is no hard evidence as to when best to test someone who is asymptomatic. And had an exposure. But the epidemiological evidence, the data that we see suggest that it really should be five to seven days after exposure. The other pitfall with this is what constitutes an exposure. The exposure really requires some time with someone who's infected. And that time right now is 15 minutes. Initially, we thought it was 15 minutes at one time, but we now know that it's 15 minutes, total time over a day.

So, if you are with someone who is contagious and is capable of infecting If you are eating dinner with them for 15 minutes. That's an exposure. But if you were in an elevator with them and both of you were masked and the total amount of time was less than five minutes.

Then that doesn't constitute an exposure.

Host: Okay. Another really, this is really informative. So I had no idea what an exposure. Was classified as, so that makes a ton of sense to me. So am I go to the grocery store and I walked past somebody. In the juice aisle. And we both had masks on. Hey, I really low risk of catching anything, but if I'm at a dinner party or I'm having a conversation, unmasks with somebody for 15 minutes in a closed room, that's an exposure.

Dr. Christopher Chao: Exactly. What we've been seeing is that patients are doing their due diligence. They all wearing the mask. They all following social distance guidelines. Well one slip-up and that's all it takes. This virus doesn't care. It is a infecting machine. It doesn't give you a Mulligan. For example, we would have someone who was hosting.

A family get together. And they all wear masks. They all follow a social distance guidelines. And then five days later, what are the family members comes in sick because another one was sick. And we go. Did you follow a social distance guidelines? Yes. All the time. Yes. Can you think of any time when you didn't wear masks and they go?

Well, we had dinner outside. We put the tables. Oh, well, we had a family picture. And we took off our masks got a group photo. There you have it. doesn't take, but one flip up.

For this virus to infect and that's, what's so challenging and that's, what's so hard to convey.

you have an office. And everyone wears masks. Where's the weak link. Everyone Paul's into the break room at 12 o'clock, six of them sit at a table. They take off their masks. They have lunch together.

That's where you're getting the transmission.

Host: Right. So when we hear it's the family gatherings, because you feel safe and taking the mask off with your family members and. Nobody has any symptoms. Somebody could be a symptomatic cause they were at a bar three nights ago with college kid in their home now. And bam, that's how it happens.

Dr. Christopher Chao: Correct. The other important point is that you hear gatherings of certain Pfizer. Right. Initially in the infection, they were like, well, you want to limit gatherings, avoid gatherings of 50 people or more. Now it's 10 people. Well, that number is based on the actual prevalence. Of the virus in the community. Initially in the infection. Window was still very little virus in the community. I would say that. Maybe less than 3% or 4% of the community. Had COVID. But now the virus is so widespread and so embedded in the community that honestly, even a party, five of Penn may not be safe. We are seeing. Party size of the four or five. And a patient gets. Infected because someone at a party of four or five was infected. So as the virus becomes more and more widespread, the probability of encountering someone who has COVID increases with group size. So even though public health officials. put a number based on. Very good calculations done by people who crunch numbers.

But all it takes is one or two. when you start seeing patients who have. Colder positive test and are symptomatic. We're now starting to see situations where they went out with their friends. They had lunch with a family member. And they were infected. So really it's understanding risk and understanding how this virus is transmitted. It requires relative close contact for a minimum duration of time. Like you said. Going to the grocery store and passing someone in the bread aisle with masks is not an exposure. If you're walking down the sidewalk at a park and there's people passing you. And you're passing each other briefly. That's not an exposure. If you get into an elevator. With someone. And everyone's mast and provided the elevator doesn't break or stall out. That's not an exposure. But what we overlook and let her guard down is when we. Have dinner or we're talking to her neighbor, you don't realize. How much time you're spending doing that. And you don't realize that the probability of a random person that's been infected as much higher than it was six months ago.

Host: Yeah, that makes a lot of sense and really draws a really clear picture of our risks and what we need to watch out for. And you even mentioned, we're taking our masks off to take a picture. So if we're all crowded around each other for five minutes, while they're taking a quick picture, even that five minutes is dangerous. If we're in close quarters with somebody inside a house.

Dr. Christopher Chao: Yes, it's risk right there is that probability. Obviously, the longer time you spend with someone to play the risk, because they're breathing out. Particles that contain virus and you're breathing it in. And we will buy masks are very beneficial, is because the calls Basque actually acts as a barrier to minimize the amount of infectious particles that are split.

A common question. I get asked as well. If a viral particle is really, really, really, really small. Doesn't it just go right through the mask. And that's actually a really good question. The answer to that is, is that. In COVID. The SARS cov two virus. Doesn't free float through the air or what we call aerosolization it actually piggybacks on droplets.

Or, when someone sneezes, you have these little Droplet. So the virus actually piggybacks on these droplets and directionally larger particles and they affected, we get hung up or stopped by a mask. do all respiratory illnesses or the actual virus or the pathogen can free float in the air? An example of that is actually measles. But fortunately for us. COVID or SARS COVID two. Doesn't aerosolize the one exception of that is in the medical. Situation where someone's being intubated or getting nebulizer treatments. That premier can Aerosolized the virus. And if the virus is aerosolized, that's when you need an N 95 mask. But if the virus is not aerosolized, or if it's just in droplets, then the cloth mask is sufficient to prevent infection.

Host: So there you go. The importance of wearing masks, even a cloth mask. can really mitigate your risk of catching COVID-19. Well, Dr. Chow, this has been fascinating. You have answered a lot of questions. And really cleared up a lot of confusion. And I hope as you said, at the beginning, we have helped a lot of people understand this better and help people understand their risk of catching COVID-19 doctor chow. Really informative. Thank you again for your time.

Dr. Christopher Chao: Thank you bill. And if anyone has any questions. Or if they have any concerns, please communicate and talk to your primary care provider or your healthcare team. We are there for you. We want to answer these questions for you because the informed patient. Is better for everyone.

Host: And will help reduce the spread as well. Which is really important. All right, Dr. Chow, thank you again. We really appreciate it.

Dr. Christopher Chao: Thank you.

Host: That's Dr. Christopher chow. And to learn more about WakeMeds urgent care services, please visit wake med.org. And if you found this podcast helpful, please share it on your social channels and check out the full podcast library for topics of interest to you. I bill clap Roth with wake med, voices brought to you by wake med health and hospitals in Raleigh, North Carolina. Thanks for listening.