Now testing is opt-out, not opt-in

[Anonymous]

Here's the American Society for Microbiology, if you don't accept Monica Gandhi as a source:

https://asm.org/Articles/2020/November/SARS-CoV-2-Testing-Sensitivity-Is-Not-the-Whole-St

[Anonymous]

And here's the math laid out, from a prior thread, if you are into that sort of thing:


Also note that this is saying that MATHMATICALLY, when you've got 50% of your population truly having the disease and a 95.1% testing specificity, more than half of your positives will be false positives.

https://www.statsdirect.com/help/clinical_epidemiology/screening_test.htm

[Anonymous]

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:Does anyone have a source on the false positive rate for these tests? Genuine question. There are lots of anecdotes like rice university, and the two “fleeting contact” people in the Australia outbreak, but is there any robust data on it?

It's not enough for you that a DCUM poster saw it on FB or heard about it on another forum? You want "DATA"!!!???

Kidding of course. Welcome to the DCUM echo chamber.

Research/explanation/support from experts has been provided already on this thread, and on the linked thread. People just don’t bother to read a thread.

The article quoted as research support is based on data from last April, prior to Delta. You'd need to take into account the much higher contagion rate of delta, which would negate some of her statements about transmissibility.

Additionally, the research does not refer to the particular test being given and its false positive rate. You have to assume there might have been advances in both the testing itself and the accuracy of the false negative or positive measurements. I want to know what exactly those rates are for that test specifically.

The article mentions a "saliva PCR" test, which is what DCPS is using.

Not all tests are the same; you need to know the manufacturer. For example, the Binax and the Ellume rapid at-home tests have different false positive and false negative rates.

Also, statistically, the choice to tighten up on false positives means more false negatives, and vice versa.

For medical tests, generally false negatives are considered a bigger problem — you don’t want to miss an actual case, while positives can just be retested for confirmation.

[Anonymous]

Anonymous wrote:What is the current rate in DC? Is it a low rate?

DC is in the category “substantial spread” according to CDC. Only other category is “high.” Over the past month, the daily case rate has doubled.

[Anonymous]

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:Does anyone have a source on the false positive rate for these tests? Genuine question. There are lots of anecdotes like rice university, and the two “fleeting contact” people in the Australia outbreak, but is there any robust data on it?

It's not enough for you that a DCUM poster saw it on FB or heard about it on another forum? You want "DATA"!!!???

Kidding of course. Welcome to the DCUM echo chamber.

Research/explanation/support from experts has been provided already on this thread, and on the linked thread. People just don’t bother to read a thread.

The article quoted as research support is based on data from last April, prior to Delta. You'd need to take into account the much higher contagion rate of delta, which would negate some of her statements about transmissibility.

Additionally, the research does not refer to the particular test being given and its false positive rate. You have to assume there might have been advances in both the testing itself and the accuracy of the false negative or positive measurements. I want to know what exactly those rates are for that test specifically.

The article mentions a "saliva PCR" test, which is what DCPS is using.

Not all tests are the same; you need to know the manufacturer. For example, the Binax and the Ellume rapid at-home tests have different false positive and false negative rates.

Also, statistically, the choice to tighten up on false positives means more false negatives, and vice versa.

For medical tests, generally false negatives are considered a bigger problem — you don’t want to miss an actual case, while positives can just be retested for confirmation.

Yes, we know. We don't know the specific tests that DCPS is using, we just now -- according to the consent form -- that they are saliva PCR. As noted, in the research cited above, even tests with what one would think of as a "good" efficiency rate (like 95%) are still problematic for false positives in a "low" prevalence setting (where "low" is what we have in DC now) (notably, even double what we have now, you'd still have a majority of your positive tests be false positives).

[Anonymous]

Anonymous wrote:

Anonymous wrote:What is the current rate in DC? Is it a low rate?

DC is in the category “substantial spread” according to CDC. Only other category is “high.” Over the past month, the daily case rate has doubled.

Is the PREVALENCE more than 50%? That's what would be considered "not low" for the purposes of the false positivity math.

[Anonymous]

Per usual, no one is actually looking at the research posted, despite asking for it.

[Anonymous]

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:What is the current rate in DC? Is it a low rate?

DC is in the category “substantial spread” according to CDC. Only other category is “high.” Over the past month, the daily case rate has doubled.

Is the PREVALENCE more than 50%? That's what would be considered "not low" for the purposes of the false positivity math.

https://coronavirus.dc.gov/page/reopening-metrics

[Anonymous]

Here's research from a "low prevalence" hospital setting. Note this is using the gold star covid test (RT-PCR), and even there, 26/31 positive results were "false positives". (Note they did 5,110 tests, and only got 31 positive results.)

https://www.dcurbanmom.com/jforum/posts/reply/120/996948.page

[Anonymous]

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:What is the current rate in DC? Is it a low rate?

DC is in the category “substantial spread” according to CDC. Only other category is “high.” Over the past month, the daily case rate has doubled.

Is the PREVALENCE more than 50%? That's what would be considered "not low" for the purposes of the false positivity math.

https://coronavirus.dc.gov/page/reopening-metrics

So....no, if positivity rate is an indication of prevalence.

[Anonymous]

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:Does anyone have a source on the false positive rate for these tests? Genuine question. There are lots of anecdotes like rice university, and the two “fleeting contact” people in the Australia outbreak, but is there any robust data on it?

It's not enough for you that a DCUM poster saw it on FB or heard about it on another forum? You want "DATA"!!!???

Kidding of course. Welcome to the DCUM echo chamber.

Research/explanation/support from experts has been provided already on this thread, and on the linked thread. People just don’t bother to read a thread.

The article quoted as research support is based on data from last April, prior to Delta. You'd need to take into account the much higher contagion rate of delta, which would negate some of her statements about transmissibility.

Additionally, the research does not refer to the particular test being given and its false positive rate. You have to assume there might have been advances in both the testing itself and the accuracy of the false negative or positive measurements. I want to know what exactly those rates are for that test specifically.

The article mentions a "saliva PCR" test, which is what DCPS is using.

Not all tests are the same; you need to know the manufacturer. For example, the Binax and the Ellume rapid at-home tests have different false positive and false negative rates.

Also, statistically, the choice to tighten up on false positives means more false negatives, and vice versa.

For medical tests, generally false negatives are considered a bigger problem — you don’t want to miss an actual case, while positives can just be retested for confirmation.

Yes, we know. We don't know the specific tests that DCPS is using, we just now -- according to the consent form -- that they are saliva PCR. As noted, in the research cited above, even tests with what one would think of as a "good" efficiency rate (like 95%) are still problematic for false positives in a "low" prevalence setting (where "low" is what we have in DC now) (notably, even double what we have now, you'd still have a majority of your positive tests be false positives).

We actually do know the specific tests that DCPS is using. It's right at the top of the opt-out form:

www.shieldt3.com/k12/

I couldn't find a specific number for their false positive rate on their website though, except that they claim that it is "very low". That could be 1-2%, which would would still be an issue for the statistics of false positives.

[Anonymous]

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:Does anyone have a source on the false positive rate for these tests? Genuine question. There are lots of anecdotes like rice university, and the two “fleeting contact” people in the Australia outbreak, but is there any robust data on it?

It's not enough for you that a DCUM poster saw it on FB or heard about it on another forum? You want "DATA"!!!???

Kidding of course. Welcome to the DCUM echo chamber.

Research/explanation/support from experts has been provided already on this thread, and on the linked thread. People just don’t bother to read a thread.

The article quoted as research support is based on data from last April, prior to Delta. You'd need to take into account the much higher contagion rate of delta, which would negate some of her statements about transmissibility.

Additionally, the research does not refer to the particular test being given and its false positive rate. You have to assume there might have been advances in both the testing itself and the accuracy of the false negative or positive measurements. I want to know what exactly those rates are for that test specifically.

The article mentions a "saliva PCR" test, which is what DCPS is using.

Not all tests are the same; you need to know the manufacturer. For example, the Binax and the Ellume rapid at-home tests have different false positive and false negative rates.

Also, statistically, the choice to tighten up on false positives means more false negatives, and vice versa.

For medical tests, generally false negatives are considered a bigger problem — you don’t want to miss an actual case, while positives can just be retested for confirmation.

Yes, we know. We don't know the specific tests that DCPS is using, we just now -- according to the consent form -- that they are saliva PCR. As noted, in the research cited above, even tests with what one would think of as a "good" efficiency rate (like 95%) are still problematic for false positives in a "low" prevalence setting (where "low" is what we have in DC now) (notably, even double what we have now, you'd still have a majority of your positive tests be false positives).

We actually do know the specific tests that DCPS is using. It's right at the top of the opt-out form:

www.shieldt3.com/k12/

I couldn't find a specific number for their false positive rate on their website though, except that they claim that it is "very low". That could be 1-2%, which would would still be an issue for the statistics of false positives.

Thank you! I missed that.

[Anonymous]

For those who don't like the date of April, 2020, here's another article from infectious disease specialists from July, 2021:

https://www.usnews.com/news/health-news/articles/2021-07-14/why-covid-19-screening-should-be-used-sparingly-in-schools

Why We Shouldn’t Blindly Screen Students for COVID-19 This Fall
When case rates are low, the majority – and sometimes even the vast majority – of positive test results are false-positives.

The DESE testing program and others across the state and across the country have shown us that the probability of COVID-19 in asymptomatic students attending in-person learning was consistently low – less than 0.5% – even before widespread vaccination. Using 0.5 as a (very) generous overestimate and a close-to-perfect (99% specific) diagnostic test, that means for every one true positive test, three will be false-positive. The true specificity of some polymerase chain reaction (PCR) tests is probably closer to 95% (in other words, still very good, but not quite so close to perfect). This more realistic estimate increases the proportion of false-positives test results even more – up to 14 false-positives for every real case of COVID-19 identified by the screening program. As case rates continue to decline, the ratio of real cases to false-positives only gets worse (and worse). Assuming a rate of 1 in 1,000 or 0.1% and a nearly perfect test, there are 14 false-positive tests for every real case found by a screening testing program, and 71 if we use the more realistic estimate of 95% specificity.

[Anonymous]

Is doing a 10% weekly population sample “blindly testing” though?

If you do no testing the prevalence will of course appear much lower. But having a weekly sample dc can track over time if one week there are twice as many positives. That seems to be important to know on a population scale.

[Anonymous]

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:Does anyone have a source on the false positive rate for these tests? Genuine question. There are lots of anecdotes like rice university, and the two “fleeting contact” people in the Australia outbreak, but is there any robust data on it?

It's not enough for you that a DCUM poster saw it on FB or heard about it on another forum? You want "DATA"!!!???

Kidding of course. Welcome to the DCUM echo chamber.

Research/explanation/support from experts has been provided already on this thread, and on the linked thread. People just don’t bother to read a thread.

The article quoted as research support is based on data from last April, prior to Delta. You'd need to take into account the much higher contagion rate of delta, which would negate some of her statements about transmissibility.

Additionally, the research does not refer to the particular test being given and its false positive rate. You have to assume there might have been advances in both the testing itself and the accuracy of the false negative or positive measurements. I want to know what exactly those rates are for that test specifically.

The article mentions a "saliva PCR" test, which is what DCPS is using.

Not all tests are the same; you need to know the manufacturer. For example, the Binax and the Ellume rapid at-home tests have different false positive and false negative rates.

Also, statistically, the choice to tighten up on false positives means more false negatives, and vice versa.

For medical tests, generally false negatives are considered a bigger problem — you don’t want to miss an actual case, while positives can just be retested for confirmation.

Yes, we know. We don't know the specific tests that DCPS is using, we just now -- according to the consent form -- that they are saliva PCR. As noted, in the research cited above, even tests with what one would think of as a "good" efficiency rate (like 95%) are still problematic for false positives in a "low" prevalence setting (where "low" is what we have in DC now) (notably, even double what we have now, you'd still have a majority of your positive tests be false positives).

We do know the specific tests. DCPS has announced elsewhere. They are SHiELD Saliva tests