Just a quick note. I’m working clinically today so I probably won’t have time to respond to you comments and questions until this evening. But keep them coming and I’ll be back later! -Jeremy
Can you please cite any studies you've found that investigate the correlation between antigen test positivity and infectivity? Do they really capture the super-spreading window or do they lag? Does "faintly" positive indicate low infectivity?
We know people are infectious when presymptomatic and symptomatic, and we know that the antigen tests are now often taking 3-5 days after symptoms begin to turn positive, so I would be concerned about missing that window if we rely on antigen tests.
When we really want to know, we use a home NAAT test made by CUE. What are your thoughts on the superiority of these and other highly sensitive tests to predict ihow contagious someone is?
Hi Clark, sorry for delay. Clinical work was a lot!
So, I do not believe there is much reason to think that there might be a lag on antigen test positivity and how contagious that person is. The whole thing is that we are detecting surface antigen of the virus itself from the nose. It's quite direct.
In terms of the disagreement between symptoms and antigen test postivity: I think that is a moving target and it depends on each person and their precise immune history. If you have just been vaccinated vs not, how many prior infections, how many of those were similar to current variant. I do think that the timing is variable in terms of days. That said, in the moment, the rapid test means a lot.
I think the CUE test does get you an answer SOONER. The question is how much sooner? It's expensive. But if you want reassurance (or diagnosis) before the rapid test, I think the CUE has value. Whether it gives you info 1 hour or 72 hours earlier, I can't say.
Reading this detailed "synopsis" on effects of proper ventilation and possible relationship to exposure and spread of COVID (let alone other viruses), makes me wonder if anyone else is actually engaged in important research related to this subject who also have a budget and paid staff to help? Thanks for your dedication/obsession. Also using this to thank you for your recent interview of 2 other docs on the important subject of the loss of Affirmative Action in terms of negative impact on needed mentorship of incoming docs who are Black or Latino/Latina let alone the patients who are Black or Latino/Latina. It is a problem I see all the time living in a MA city that is over 50% Latina/Latino. Now exacerbated by no protections of Affirmative Action. Same problem exists in our public education system, by the way.
I think the rapid testing experts (producers) are looking but a lot of the issue is that the FDA does not seem willing (yet) to assess rapids in this way, despite very promising science in the medical literature on this topic.
Glad you watched the Q&A with Drs. Essien and Opara. I mentioned it in the Friday Five, I'm sure you saw :)
Early in the pandemic I read about a company working on a device that could detect viruses in the air, so a place like a hospital or airport could rapidly screen every person entering the facility. They claimed they had proof of concept and would run larger trials Real Soon Now.
But the silence has been deafening for a few years. Dunno if they just ran out of funds or their tech turned out not to work or what.
But if we had such a device it could be game changing.
Great question. There are devices that do this. The REALLY interesting this is that in many situations, you can swab SURFACES and get a good idea about the air. While we understand that the virus spread is not mainly via surfaces, it has to go somewhere. And it tends to fall to the ground. So some companies were testing desks in offices as a way of understanding what is in the air around it. That's probably a cheaper way of doing this. And it worked, btw; these companies found virus on desks a few days before the occupants tested positive; I learned about this at the White House air quality summit. Indeed some of the funding on this stuff dried up.
Interesting take. My curiosity is about the super-shedders. Early on in the pandemic, there was quite a bit of discussion about this phenomenon. At the time, I believe that the assumption was that some individuals had a far greater maximum amount of virus shed, that is that the total amount shed during an infection varied by orders of magnitude among different individuals. From Marc Johnson's research tracking variants in wastewater, I gather some individuals can shed something like five or six orders of magnitude more (non-transmissible) virus from their gut than average.
Has there been research to indicate one way or the other on this issue for respiratory transmission?
Great comments/questions here - thanks to all for the insights.
Great question. I think the air on planes is really good. The issue is that you're within very close proximity to 5-10 people and the air exchange might not suffice for that. But because the air is so good on planes, you can worry less about someone coughing 5 rows away from you. The restroom is also another one where you will see tons of virus. So, I do mask on planes for the most part because when else am I sitting near 5-10 strangers for 2-10 hours?
But it may be that the airport itself (certain parts) is more of a risk than the plane!
Clark Kent has some very good questions about antigen tests that I hope you'll respond to. I have been doubtful for a long time about their value since they apparently produce so many false negatives when somebody is infectious. And what about the alternative test he mentions?
I responded above. I do not believe there are data to show false negatives *when someone is contagious*. They miss the early infection. So the danger is testing rapid negative on day 1, thinking you are fine on day 2-4 (and not testing again), when in fact you turned positive on day 2 or 3. The CUE test gets you an answer on infection sooner. I just don't know how many hours before the rapid it gains.
I always educate to test with the rapid antigen test when not feeling well. If they test negative, I also tell them they need to retest in 48 hours. If they are positive testing 48 hours later has shown a positive reaction. When testing in the schools, the kids rapid antigen test turn positive immediately. They are also sick with either a fever and or cough. Breaks my heart each time!
***Hi all***
Just a quick note. I’m working clinically today so I probably won’t have time to respond to you comments and questions until this evening. But keep them coming and I’ll be back later! -Jeremy
Can you please cite any studies you've found that investigate the correlation between antigen test positivity and infectivity? Do they really capture the super-spreading window or do they lag? Does "faintly" positive indicate low infectivity?
We know people are infectious when presymptomatic and symptomatic, and we know that the antigen tests are now often taking 3-5 days after symptoms begin to turn positive, so I would be concerned about missing that window if we rely on antigen tests.
When we really want to know, we use a home NAAT test made by CUE. What are your thoughts on the superiority of these and other highly sensitive tests to predict ihow contagious someone is?
Thank you!
Hi Clark…See above. I’ll reply tonight. Cheers.
Hi Clark, sorry for delay. Clinical work was a lot!
So, I do not believe there is much reason to think that there might be a lag on antigen test positivity and how contagious that person is. The whole thing is that we are detecting surface antigen of the virus itself from the nose. It's quite direct.
In terms of the the faintness = low infectivity, there are many studies on this. This one is good: https://pubmed.ncbi.nlm.nih.gov/35348350/
Another good one is linked in my essay.
In terms of the disagreement between symptoms and antigen test postivity: I think that is a moving target and it depends on each person and their precise immune history. If you have just been vaccinated vs not, how many prior infections, how many of those were similar to current variant. I do think that the timing is variable in terms of days. That said, in the moment, the rapid test means a lot.
I think the CUE test does get you an answer SOONER. The question is how much sooner? It's expensive. But if you want reassurance (or diagnosis) before the rapid test, I think the CUE has value. Whether it gives you info 1 hour or 72 hours earlier, I can't say.
Thx!
Reading this detailed "synopsis" on effects of proper ventilation and possible relationship to exposure and spread of COVID (let alone other viruses), makes me wonder if anyone else is actually engaged in important research related to this subject who also have a budget and paid staff to help? Thanks for your dedication/obsession. Also using this to thank you for your recent interview of 2 other docs on the important subject of the loss of Affirmative Action in terms of negative impact on needed mentorship of incoming docs who are Black or Latino/Latina let alone the patients who are Black or Latino/Latina. It is a problem I see all the time living in a MA city that is over 50% Latina/Latino. Now exacerbated by no protections of Affirmative Action. Same problem exists in our public education system, by the way.
Lyn,
I think the rapid testing experts (producers) are looking but a lot of the issue is that the FDA does not seem willing (yet) to assess rapids in this way, despite very promising science in the medical literature on this topic.
Glad you watched the Q&A with Drs. Essien and Opara. I mentioned it in the Friday Five, I'm sure you saw :)
Early in the pandemic I read about a company working on a device that could detect viruses in the air, so a place like a hospital or airport could rapidly screen every person entering the facility. They claimed they had proof of concept and would run larger trials Real Soon Now.
But the silence has been deafening for a few years. Dunno if they just ran out of funds or their tech turned out not to work or what.
But if we had such a device it could be game changing.
Great question. There are devices that do this. The REALLY interesting this is that in many situations, you can swab SURFACES and get a good idea about the air. While we understand that the virus spread is not mainly via surfaces, it has to go somewhere. And it tends to fall to the ground. So some companies were testing desks in offices as a way of understanding what is in the air around it. That's probably a cheaper way of doing this. And it worked, btw; these companies found virus on desks a few days before the occupants tested positive; I learned about this at the White House air quality summit. Indeed some of the funding on this stuff dried up.
Hi Jeremy, sorry but I don't know what you're referencing in "see above". Thanks!
replied now :)
Interesting take. My curiosity is about the super-shedders. Early on in the pandemic, there was quite a bit of discussion about this phenomenon. At the time, I believe that the assumption was that some individuals had a far greater maximum amount of virus shed, that is that the total amount shed during an infection varied by orders of magnitude among different individuals. From Marc Johnson's research tracking variants in wastewater, I gather some individuals can shed something like five or six orders of magnitude more (non-transmissible) virus from their gut than average.
Has there been research to indicate one way or the other on this issue for respiratory transmission?
Great comments/questions here - thanks to all for the insights.
Have heard that air exchange in planes is quite high. Sometimes up to every 6 min. Do you mask when flying? 🧐
Great question. I think the air on planes is really good. The issue is that you're within very close proximity to 5-10 people and the air exchange might not suffice for that. But because the air is so good on planes, you can worry less about someone coughing 5 rows away from you. The restroom is also another one where you will see tons of virus. So, I do mask on planes for the most part because when else am I sitting near 5-10 strangers for 2-10 hours?
But it may be that the airport itself (certain parts) is more of a risk than the plane!
I always mask when flying. In the airport too.
Clark Kent has some very good questions about antigen tests that I hope you'll respond to. I have been doubtful for a long time about their value since they apparently produce so many false negatives when somebody is infectious. And what about the alternative test he mentions?
Will reply tonight (see my comment above). Thank you!
I responded above. I do not believe there are data to show false negatives *when someone is contagious*. They miss the early infection. So the danger is testing rapid negative on day 1, thinking you are fine on day 2-4 (and not testing again), when in fact you turned positive on day 2 or 3. The CUE test gets you an answer on infection sooner. I just don't know how many hours before the rapid it gains.
I always educate to test with the rapid antigen test when not feeling well. If they test negative, I also tell them they need to retest in 48 hours. If they are positive testing 48 hours later has shown a positive reaction. When testing in the schools, the kids rapid antigen test turn positive immediately. They are also sick with either a fever and or cough. Breaks my heart each time!