Antibody test accuracy and immunity passports

SteveAWOL

Distinguished Member
Looks like even when the UK finally achieves 100,000 tests per day we’ll still have thousands of people being incorrectly diagnosed, as whatever the NHS eventually end up using will provide similar accuracy to the antibody tests recently approved by the FDA over in USA.

This Cellex test has a "sensitivity" of 93.8% so of those who have actually been infected 6.2% will receive a false-negative result and end up self isolating unnecessarily.

Whilst the "specificity" of 95.6% means a false-positive rate of 4.4% and these individuals could be considered eligible for the “immunity passports“ despite never having been infected with SARS-CoV-2.

So if the proportion of general population who are infected is actually 1% then Bayes Theorem shows that 82% of positive results will in fact be false, meaning thousands of people every day potentially being lead to believe they’re immune when they’ve yet to be infected :eek:


1586853469424.jpeg
 

kenshingintoki

Distinguished Member
Yeah, the 70% sensitive swab we've been using here is really not going to help with immunity passports etc.

Work (NHS) phoned me up a few days ago asking if I'd like to be tested. They noted that the test they're using is really only effective at identifying people between days 1 to 4 of illness.

So although our testing capacity for what we have today might be increasing; we're still extremely far away from the holy grail.
 
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richp007

Distinguished Member
This doesn't look that great does it?!

One area of all this where I've not really delved. But was hoping for something more clinical than this.
 

SteveAWOL

Distinguished Member
Professor Sikora‘s latest update on the antibody testing of staff at Rutherford Cancer Centres...


 

GadgetObsessed

Well-known Member
Looks like even when the UK finally achieves 100,000 tests per day we’ll still have thousands of people being incorrectly diagnosed, as whatever the NHS eventually end up using will provide similar accuracy to the antibody tests recently approved by the FDA over in USA.

This Cellex test has a "sensitivity" of 93.8% so of those who have actually been infected 6.2% will receive a false-negative result and end up self isolating unnecessarily.

Whilst the "specificity" of 95.6% means a false-positive rate of 4.4% and these individuals could be considered eligible for the “immunity passports“ despite never having been infected with SARS-CoV-2.

So if the proportion of general population who are infected is actually 1% then Bayes Theorem shows that 82% of positive results will in fact be false, meaning thousands of people every day potentially being lead to believe they’re immune when they’ve yet to be infected :eek:


View attachment 1281770
If those figures are correct then the test is surprisingly accurate. (Compared to many other medical diagnostic tests.)
 

SteveAWOL

Distinguished Member
So even when reliable antibody tests are widely available we still don’t yet know what quantity of antibodies are required to provide immunity to this novel virus or how long it’ll last... and some people’s innate immune system might repel SARS-COV-2 without the need for antibodies!!



 

SteveAWOL

Distinguished Member
Roche and Abbott receiving emergency approval from EU and FDA for their antibody tests which claim to have accuracy and specificity of 99%

 

simonblue

Distinguished Member
Looks like one has been approved :smashin:


 

Ste7en

Distinguished Member
It sounds pretty good as well. Also reporting that antibodies could protect for up to three years.

We could do with some good news.
 

SteveAWOL

Distinguished Member


 
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