Anonymous wrote:

Anonymous wrote:

Anonymous wrote: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.

Thank you for posting this article.

That article is pre-Delta and describes an environment of declining case rates.

Anonymous wrote:

Anonymous wrote:

Anonymous wrote: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.

Thank you for posting this article.

That article is pre-Delta and describes an environment of declining case rates.

Anonymous wrote:

Anonymous wrote: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.

Thank you for posting this article.

Anonymous wrote: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 wrote:Why do people keep saying stuff like “DC is idiotic about testing”?

DC has done a great job of Covid testing! I have a lot of complaints about DC government, but I’ve only been impressed with their Covid testing set-up. Easy to access, efficient, and accurate.

Anonymous wrote:Why do people keep saying stuff like “DC is idiotic about testing”?

DC has done a great job of Covid testing! I have a lot of complaints about DC government, but I’ve only been impressed with their Covid testing set-up. Easy to access, efficient, and accurate.

Anonymous wrote:

Anonymous wrote:Shield test's negativity (or "specificity") rate is 98.9%, according to themselves (slide 4): https://www.iasaedu.org/cms/lib/IL01923163/Centricity/Domain/4/SHIELD%20IL%20IDPH%20overview%20050621.pdf

That means that the test correctly returns a negative result 98.9% of the time when the person is truly negative, and returns a "false positive" 1.1% of the time.

The Washington Post article posted earlier:

"Rapid antigen and saliva PCR tests, which are frequently used in schools, can have a false positive rate of 1 or 2 percent. That may sound low, but statisticians know that, when testing in a setting of low prevalence of disease, even a single-digit false-positive rate can be extremely problematic."

This study uses a slightly less specific test (the BinaxNow rapid test), which has a specificity of 98.5% (https://abbott.mediaroom.com/2020-08-26-Abbotts-Fast-5-15-Minute-Easy-to-Use-COVID-19-Antigen-Test-Receives-FDA-Emergency-Use-Authorization-Mobile-App-Displays-Test-Results-to-Help-Our-Return-to-Daily-Life-Ramping-Production-to-50-Million-Tests-a-Month)

The ASM study shows that with a similar test specificity, and low PREVALENCE rates (0.1% to 1.0%), the percentage of positive tests that are false is between 60 and 94% (it's lower when the prevalence is higher). https://asm.org/Articles/2020/November/SARS-CoV-2-Testing-Sensitivity-Is-Not-the-Whole-St

SO WHAT IS PREVALENCE DURING DELTA?

During delta and with twice weekly testing (so a lot of tests), the UK found a prevalence rate in schools of 0.27% in primary schools and 0.42% in secondary schools in June, 2021. Note that they didn't mask, and don't have vaccination approval for the 12-15 year olds. They did of course do other mitigation measures related to the testing. I offer this as it seems to be one of the only studies of PREVALENCE in schools, during delta, where there was lots of testing. https://www.gov.uk/government/news/covid-19-study-finds-lower-prevalence-in-schools

PREVALENCE outside of schools in the UK during early delta (June 24 to July 12) was 0.63%. (https://www.medicalnewstoday.com/articles/covid-19-in-england-rising-infections-as-delta-variant-takes-hold#Delta-surge).

How does that PREVALENCE compare to covid CASE RATES (which is what we all obsessively look at in DC)? Between June 24 and July 12, UK’s 7-day case rates per 100,000 went from 145 to 358 (https://coronavirus.data.gov.uk/details/cases). In DC terms (of cases per day instead of 7 days) that is about 20/100,000 per day to 51/100,000 per day.

The point being that we likely have low prevalence + Probably even lower in schools as that's been true consistently + test has a specificity greater than 1% = whole lot of false positives.

Sigh. Didn’t even look at this particular test’s specificity plus secondary testing by this lab as a mitigant for false positives. DC has actually entered into a pretty promising relationship here. Wish it was better publicized though.

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:I hope this leads to a "test and stay" policy, where instead of quarantining, kids can just get tested every day. UK found that this was equally as effective as quarantine.

https://www.ox.ac.uk/news/2021-07-23-daily-contact-covid-19-testing-students-effective-controlling-transmission-schools

This is really what they need to do. Statistically, most positives will be false.

Yeah, I would be for asymptomatic random testing if DC wasn't idiotic about testing.

Ditto. If they did test and stay I would not opt out. But I’m opting out. If kid is actually ill I will test. Oh what is that you say — most kids have no symptoms?! Hmmm. Sounds like they are fine to go to school.

Anonymous wrote:We opted out. My 16 year old son has been double Vaxxed for months and will get a booster when it’s his turn. He masks. He is mindful of distancing and washing hands and being alert to those around him who might be coughing or yelling (spewing particles). I don’t trust the schools to give the tests properly or have the results tested properly or to have the correct student’s results associated with the correct student.

Anonymous wrote:We opted out. My 16 year old son has been double Vaxxed for months and will get a booster when it’s his turn. He masks. He is mindful of distancing and washing hands and being alert to those around him who might be coughing or yelling (spewing particles). I don’t trust the schools to give the tests properly or have the results tested properly or to have the correct student’s results associated with the correct student.

Anonymous wrote:Shield test's negativity (or "specificity") rate is 98.9%, according to themselves (slide 4): https://www.iasaedu.org/cms/lib/IL01923163/Centricity/Domain/4/SHIELD%20IL%20IDPH%20overview%20050621.pdf

That means that the test correctly returns a negative result 98.9% of the time when the person is truly negative, and returns a "false positive" 1.1% of the time.

The Washington Post article posted earlier:

"Rapid antigen and saliva PCR tests, which are frequently used in schools, can have a false positive rate of 1 or 2 percent. That may sound low, but statisticians know that, when testing in a setting of low prevalence of disease, even a single-digit false-positive rate can be extremely problematic."

This study uses a slightly less specific test (the BinaxNow rapid test), which has a specificity of 98.5% (https://abbott.mediaroom.com/2020-08-26-Abbotts-Fast-5-15-Minute-Easy-to-Use-COVID-19-Antigen-Test-Receives-FDA-Emergency-Use-Authorization-Mobile-App-Displays-Test-Results-to-Help-Our-Return-to-Daily-Life-Ramping-Production-to-50-Million-Tests-a-Month)

The ASM study shows that with a similar test specificity, and low PREVALENCE rates (0.1% to 1.0%), the percentage of positive tests that are false is between 60 and 94% (it's lower when the prevalence is higher). https://asm.org/Articles/2020/November/SARS-CoV-2-Testing-Sensitivity-Is-Not-the-Whole-St

SO WHAT IS PREVALENCE DURING DELTA?

During delta and with twice weekly testing (so a lot of tests), the UK found a prevalence rate in schools of 0.27% in primary schools and 0.42% in secondary schools in June, 2021. Note that they didn't mask, and don't have vaccination approval for the 12-15 year olds. They did of course do other mitigation measures related to the testing. I offer this as it seems to be one of the only studies of PREVALENCE in schools, during delta, where there was lots of testing. https://www.gov.uk/government/news/covid-19-study-finds-lower-prevalence-in-schools

PREVALENCE outside of schools in the UK during early delta (June 24 to July 12) was 0.63%. (https://www.medicalnewstoday.com/articles/covid-19-in-england-rising-infections-as-delta-variant-takes-hold#Delta-surge).

How does that PREVALENCE compare to covid CASE RATES (which is what we all obsessively look at in DC)? Between June 24 and July 12, UK’s 7-day case rates per 100,000 went from 145 to 358 (https://coronavirus.data.gov.uk/details/cases). In DC terms (of cases per day instead of 7 days) that is about 20/100,000 per day to 51/100,000 per day.

The point being that we likely have low prevalence + Probably even lower in schools as that's been true consistently + test has a specificity greater than 1% = whole lot of false positives.

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. [/quote

And? Could it be more people got tested that had not even a runny nose and thought Delta - I am not vaxed! DC rates are climbing because people aren’t vaxed.