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No, as I explained, it's not. It depends who you're testing.
And as I am explaining, I am disagreeing with you.
WHAT IS THE “PERCENT POSITIVE” AND WHY DOES IT MATTER?
The percent positive is exactly what it sounds like: the percentage of all coronavirus tests performed that are actually positive, or: (positive tests)/(total tests) x 100%. The percent positive (sometimes called the “percent positive rate” or “positivity rate”) helps public health officials answer questions such as:
What is the current level of SARS-CoV-2 (coronavirus) transmission in the community?
Are we doing enough testing for the amount of people who are getting infected?
The percent positive will be high if the number of positive tests is too high, or if the number of total tests is too low. A higher percent positive suggests higher transmission and that there are likely more people with coronavirus in the community who haven’t been tested yet.
The percent positive is a critical measure because it gives us an indication how widespread infection is in the area where the testing is occurring—and whether levels of testing are keeping up with levels of disease transmission.
WHAT DOES A HIGH PERCENT POSITIVE MEAN?
A high percent positive means that more testing should probably be done—and it suggests that it is not a good time to relax restrictions aimed at reducing coronavirus transmission. Because a high percentage of positive tests suggests high coronavirus infection rates (due to high transmission in the community), a high percent positive can indicate it may be a good time to add restrictions to slow the spread of disease.
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But I thought you said, "in reality viral transmission is the same." And each of the variants has had a different transmissibility rate, e.g. Delta AY.4.2 was thought to be 10 to 20% more transmissible than Delta.
And as I am explaining, I am disagreeing with you.
There is no need to quote so called "experts." This is very common sense, and you can think through it yourself. Why do we have brains if we will just out source our thinking to others?
If we had a truly random sampling of people we were testing, then positivity would stay the same whether we did 1,000 tests or 10,000,000. That's the point of sampling.
Now if your sampling is not random, it can skew positivity in either direction no matter the number of tests you do. If your policy was to test just asymptomatic, you may get a similar positivity rate irregardless if you test 1,000 or 10 million. If you tested just hospitalized patients, you'd get a different positivity rate. Your crossection of whom you're testing is important.
The idea that as tests fall positivity goes up is not a rule, but based on the practical idea that symptomatic people would be more likely to be tested than asymptomatic people if you did less tests. That's really no longer true in 2023.
How would you distinguish between that and a common cold? Not that I think it's necessary to do so!
I swear, people have become addicted to this whole thing - including compulsively testing themselves.
Well we really wouldnt be able to distinguish but usually, if we dont feel well, we stay at home until it passes to avoid getting others sick...that said, we are rarely ever sick. The whole "testing" for Covid seems silly to me anyway, I mean I can test negative at lunch time and then be in contact with someone who is positive 10 minutes later. I think this is why some people compulsively test.
We have never taken any precaution against Covid unless mandated, but find it ironic that those around us that do take all the precautions have had Covid multiple times and I only know this because they broadcast it every time they get it.
There is no need to quote so called "experts." This is very common sense, and you can think through it yourself. Why do we have brains if we will just out source our thinking to others?
If we had a truly random sampling of people we were testing, then positivity would stay the same whether we did 1,000 tests or 10,000,000. That's the point of sampling.
Now if your sampling is not random, it can skew positivity in either direction no matter the number of tests you do. If your policy was to test just asymptomatic, you may get a similar positivity rate irregardless if you test 1,000 or 10 million. If you tested just hospitalized patients, you'd get a different positivity rate. Your crossection of whom you're testing is important.
The idea that as tests fall positivity goes up is not a rule, but based on the practical idea that symptomatic people would be more likely to be tested than asymptomatic people if you did less tests. That's really no longer true in 2023.
Aren't you a strong advocate that no testing should be done unless one has symptoms or gets sick? Now it seems that you are arguing that the statistics are skewed in favor of those that are sick and getting tested. Your position now is that random sampling people is the way to go.
Here's your previous quote,
"Yes, which is why I'm here. To offer people the other side of the coin, the limits of these labs and potential harms from relying on them too much. Like I keep repeating, the USA spends 20 billion on diagnostic labs, which is half of all what the world spends, yet the USA is 1/25 th of the world's population.
You'd expect if these diagnostic tests were really making people live longer, we'd see that reflected in the USA's LE, sadly that's not the case. More money on preventative medicine has not really produced reliable benefits."
I know there's a point that you are trying to make but it isn't really clear within the context of epidemiological surveillance techniques.
Aren't you a strong advocate that no testing should be done unless one has symptoms or gets sick? Now it seems that you are arguing that the statistics are skewed in favor of those that are sick and getting tested. Your position now is that random sampling people is the way to go.
None of that is my position. I'm explaining to her how sampling determines the positivity and not number of tests.
My position is testing is worthless for COVID19 unless you want Paxlovid. Or if you want to track COVID19 levels in the community (then just test waste water).
None of that is my position. I'm explaining to her how sampling determines the positivity and not number of tests.
My position is testing is worthless for COVID19 unless you want Paxlovid. Or if you want to track COVID19 levels in the community (then just test waste water).
It's not one option vs another but a composite depending on regional differences. Not every part of the country is the same.
"Wastewater surveillance captures the presence of SARS-CoV-2 shed by people with and without symptoms. By measuring SARS-CoV-2 levels in untreated wastewater over time, public health officials can determine if infections are increasing or decreasing in a sewershed.
Unlike other types of COVID-19 surveillance, wastewater surveillance does not depend on people having access to healthcare, people seeking healthcare when sick, or availability of COVID-19 testing."
It's not let's stop doing testing and just do wastewater testing. Experts know the evidence behind all of the methods and techniques. That's common sense.
Epidemiological projections are made with direct patient sampling and from wastewater testing. They rely on mathematical models.
Last edited by Medical Lab Guy; 02-13-2023 at 10:58 AM..
It's not one option vs another but a composite depending on regional differences. Not every part of the country is the same. .
Sampling people has the same limitation. If you want to capture more geographic locations, sample more waste water. But there is no longer a need for such fine tuned surveillance anyways. Emergency is over.
Sampling people has the same limitation. If you want to capture more geographic locations, sample more waste water. But there is no longer a need for such fine tuned surveillance anyways. Emergency is over.
Every single method has limitations which is why multiple techniques are used. The US does not have a national healthcare service. We don't have a national data base to do statistics easily with. Our healthcare is fractured into separate private and governmental providers. We have laws preventing the mining of private individual healthcare information. Adjustments have to be made.
"R0 (R naught) is the basic reproduction number, also known as basic reproduction ratio or rate which is an epidemiological metric used to measure the transmissibility of infectious agents. R0 is a derivative of the following variables—the duration of infectivity after the patient gets infected, the likelihood of transmission of infection per contact between a susceptible person and an infectious individual, and the contact rate. R0 is usually estimated retrospectively from serial epidemiological data or using theoretical mathematical models. Epidemiologists can calculate R0 using contact-tracing data, the most common method is to use cumulative incidence data. When mathematical models are used, R0 values are estimated using ordinary differential equations. R0 of COVID-19 as initially estimated by the World Health Organization (WHO) was between 1.4 and 2.4"
"Scientists say there is no evidence that the BA.5 version of the Omicron coronavirus variant is more transmissible than measles, or that it has a basic reproduction number, or “R-naught” (R0), of 18.6, which would be greater than that of measles. While BA.5 appears to be spreading faster than other Omicrons still circulating, experts say that BA.5 is unlikely to be one of “the most infectious viruses known to man,” as some have claimed."
"There are three main factors used to calculate R0. They are the infectious period of the disease, the mode of transmission, and the contact rate.Feb 7, 2020"
"Prevalence differs from incidence in that prevalence includes all cases, both new and preexisting, in the population at the specified time, whereas incidence is limited to new cases only. Point prevalence refers to the prevalence measured at a particular point in time."
One then has to determine the disease burden on resources that go far beyond simply those that are infected.
Not every person in the US is going to be tested at any single point in time at the same time. Can't be done. You will need to extrapolate using many methods and using elaborate calculations to determine the prevalence of COVID out there.
Disease surveillance as the name implies means you survey the population not only in numbers but in strains circulating. There's no start and stop with regard to surveillance. People get sick and people get tested. COVID is here to stay.
I don't know what you mean by emergency is over and how that translates to different hands on policies at an individual level. State of emergency is a governmental proclamation that gives government added resources and power is my understanding. They did give free COVID testing and kits. It did not alter epidemiological methods and tecnhiques. There is political discord that might impact funding to the NIH and the CDC which could do that.
R0 is a theoretical value that cannot be measured. It's best understood as maximum reproductive rate, if all the population is naive, but even here, it's a bit of a figment of a mathematician's imagination to get the exponential equation to fit the graph.
R is the current reproductive rate and can be measured.
Quote:
I don't know what you mean by emergency is over and how that translates to different hands on policies at an individual level. State of emergency is a governmental proclamation that gives government added resources and power is my understanding. They did give free COVID testing and kits. It did not alter epidemiological methods and tecnhiques. There is political discord that might impact funding to the NIH and the CDC which could do that.
I'm not sure what we are arguing. I take it you want more testing or keep things as? COVID19 is no longer a burden on the US healthcare system. We have no reason to track it. Many countries don't track it at all anymore.
But of course, if we want to track for academic reasons, out of an "abundance of caution" or to make the test makers richer, by all means let's keep testing.
I don't really know anyone getting tested anymore, even when they have symptoms. Most Americans have reverted to treating COVID like they do any URI.
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