Just on w @RTE_PrimeTime about rapid tests

Surprised at lack of trust the government has in the Irish ppl

Instead of supporting access to simple at-home tests to tell if u r infectious, position appears to be to limit access bc they don't trust ppl to handle a negative test

1/
We do not defeat a pandemic without properly engaging & trusting in the public

To actively advocate against an asymptomatic person to be able to access a rapid test that has a very high sensitivity to tell you if you are spreading the virus doesn't make sense.

2/
Similarly to actively want to force symptomatic ppl to NOT have access to at-home tests bc u want ensure they get a much less accessible PCR test isn't good policy. Do we want symptomatic ppl leaving home to get PCR tests?? A rapid test is accessible and fast.

3/
Overall though, there seems to be confusion among decision makers in Ireland that these tests are not sensitive

Rapid tests do a very good job at detecting you **when you are infectious** - which is what matters if you are using a rapid test.

Why is this still a question?

4/
To be clear - this confusion is global confusion. it's taken a year of discussions and far too many publications and OpEds for US FDA and CDC to begin to understand that for identifying infectiousness and limiting spread, speed and frequency are most important.

5/
If rapid test is positive and symptomatic - done deal. Government should set up voluntary single click phone-based reporting. If someone won't use the reporting b/c they don't want to be traced, they probably wouldn't have gotten the PCR too. Better to know than not know

3.1/

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More from @michaelmina_lab

11 May
FAQ: Why is a lab test w a 12-48hr delay not as useful for screening?

Simple

Even super high sensitivity lab tests have 0% sensitivity while awaiting results

So you can be @ peak viral load & superspreading virus and not be detected by a lab test while spreading for 2 days

1/
For evaluating a tests “Effective sensitivity” to help stop transmission, this 0% sensitivity while awaiting results must be taken into account since ppl live their lives while waiting on results

If a test takes 2 days to return it’s effectiveness is already reduced by 33%

2/
So w a 2 day delay, a theoretical 100% sensitivity PCR test may already be maxing out at 67% effective sensitivity to slow spread... which is what we are trying to do w screening test programs.

3/
Read 7 tweets
10 May
This is exactly why we need rapid tests and why they must be done frequently.

Viral load is not static.

At any given time, 2% of ppl carry 90% of the viral load. Who those people are changes day to day as the virus grows and falls inside ppl.

1/x
This is also why lower analytical sensitivity tests, when performed frequently, are MUCH more sensitive than very high sensitivity tests performed infrequently or w slow return of results

If infectious, you will be detected by rapid Ag tests. And that’s what matters.

2/
But if you aren’t testing frequently, you are VERY likely to miss getting a swab in your nose before or when you are at peak infectivity (bc peak is reached VERY fast and diminishes fast).

So a test that takes a long time to return or is infrequent, simply doesn’t help much.

3/
Read 4 tweets
9 May
@President_MU For an advisor to your government - you don’t appear to know what you are talking about @President_MU wrt rapid tests.

The comment adds nothing of benefit and further sows confusion.

You should be ashamed of your demeanor here.
@President_MU .@President_MU

I recognize youve heard things like “50% sensitivity”

In light of your comments it’s clear there are key pieces youve missed

Sensitivity nears 100% to catch potential superspreaders and others currently transmitting, for example.

See 👇
thelancet.com/journals/lance…
@President_MU 50% sensitivity is vs PCR. But as CDC (and hopefully you) know, PCR remains pos long after isolation & contagiousness end

Rapid Ag tests don’t stay positive past the infectious stage.

50% isn’t a lack of sensitivity of Ag... it’s a lack of specificity of PCR for infectiousness
Read 5 tweets
3 May
This is how progress is made:

A new study about to start in UK.

Can rapid tests each morning following contact w a #COVID19 positive individual be used instead of a 14 day quarantine.

I’ve been pushing for this type of study/policy for a year.

gov.uk/government/new…

1/
Why is this important??

Quarantines take a major toll on individuals. Physical and emotional. Most contacts in quarantine never become positive and there are multiple contacts for each positive.

2/
A quarantine of an uninfected individual should be considered with the same concern as false positives - and false positives sure have gotten a LOT of attention. But unlike a false positive, you currently can’t really get a “confirmatory test” to help get out of quarantine.

3/
Read 7 tweets
30 Apr
To: Scientists, Doctors and anyone writing OpEds or Making Policy Decisions about tests

PLEASE NOTE:

The number of False Positive tests does *NOT* go up when prevalence of #COVID19 goes down.

The number of False Positives is the SAME regardless of high vs low prevalence.

1/
This idea keeps getting thrown around in OpEds and by decision makers - worried false positives sky rocket once disease drops.

But if you have 10 False Pos per 100,000 tests when incidence is high, you’ll have ~10 False Positives per 100,000 tests when incidence is low.

2/
What changes is not the number of false pos results, but the fraction of all pos that may be false

Of course even if false pos rate is 0.0001 (about that of newer rapid Ag tests), if there is zero Covid, then sure, 100% of positives will be false. But it’s still only 1 in 10,000
Read 6 tweets
29 Apr
UK ppl should be concerned that head of @RoyalStatSoc #COVID19 diagnostics grp is inaccurately stating facts about testing-Intentionally conflating false positives w positive predictive value (totally different) to make rapid tests look bad #badscience
1/
In the tweet above, to get false positive rate you need to have the number of true negatives in the denominator. If you fail to do that, you aren't measuring the false positive rate. It's a totally different number. Studies show false positive rates for many tests <0.1%.

2/
In the first tweet I said "UK ppl should be concerned"... but c'mon @RoyalStatSoc - why allow this to continue. He's been stating falsehoods and bending stats or performing flagrantly unacceptable/unpublishable analyses for months now. Sowing confusion. How is this helpful?
Read 5 tweets

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