[M T]

You can't consider the two tests independent, though.

Thanks for the correction.  I will happily defer to someone who can produce the appropriate statistics.  

In the 2+1 false positives at CovidTestingProject.org were on different samples, so Stanford would have judged 3 positives. 

For the manufacturer's samples, Stanford would have judged 3 to 5 samples positive, since we don't know whether those 3 IgM + 2 IgG samples were on 3, 4, or 5 different samples.

Minimum FP rate: 3/371 + 0/30 +  3/108 = 1.18%  (3330 + 1.18% = 39.3)
Maximum FP rate: 5/371 + 0/30 + 3/108 = 1.57%   (3330 + 1.57% = 52)
(Note that I don't know whether Stanford had access to CovidTestingProject.org.  They presumably did have access to the 3 to 5 false positives by the manufacturer, but used 2.)

I wonder why Stanford didn't reveal the number of results that were positive for IgG only, IgM only, and IgG + IgM.

Indeed, with only 50 positives, and since we know they knew how to contact those with positive results, I wish they had run an independent set of the virus antibody tests on these individuals.  Didn't Stanford claim to be creating a gold standard antibody test?   They could clear this up quickly if they showed, say, 45 of their 50 positive individuals were positive on each of multiple antibody tests. 

If the manufacturer were to indicate that its 5 positives were all on different samples (not that Stanford necessarily would have known these numbers), can the Stanford study actually be showing that there is a near 0% incidence of COVID-19 in SCC?  (modulo the comments about self-selection, etc.)  Presumably, it would show some upper bound on the infection rate rather than just showing 0%.


I wonder if Stanford warned these individuals of the (low, medium, high) likelihood that their positive test could be a false positive.  I expect they warned that having antibodies didn't necessarily mean immunity.   I also kinda wonder why someone who tested positive hasn't identified themselves to the media and talked about the process and what it means to them.

[M T]

You can't consider the two tests independent, though.

Thanks for the correction.  I will happily defer to someone who can produce the appropriate statistics.  

In the 2+1 false positives at CovidTestingProject.org were on different samples, so Stanford would have judged 3 positives. 

For the manufacturer's samples, Stanford would have judged 3 to 5 samples positive, since we don't know whether those 3 IgM + 2 IgG samples were on 3, 4, or 5 different samples.

Minimum FP rate: 3/371 + 0/30 +  3/108 = 1.18%  (3330 + 1.18% = 39.3)
Maximum FP rate: 5/371 + 0/30 + 3/108 = 1.57%   (3330 + 1.57% = 52)
(Note that I don't know whether Stanford had access to CovidTestingProject.org.  They presumably did have access to the 3 to 5 false positives by the manufacturer, but used 2.)

I wonder why Stanford didn't reveal the number of results that were positive for IgG only, IgM only, and IgG + IgM.

Indeed, with only 50 positives, and since we know they knew how to contact those with positive results, I wish they had run an independent set of the virus antibody tests on these individuals.  Didn't Stanford claim to be creating a gold standard antibody test?   They could clear this up quickly if they showed, say, 45 of their 50 positive individuals were positive on each of multiple antibody tests. 

If the manufacturer were to indicate that its 5 positives were all on different samples (not that Stanford necessarily would have known these numbers), can the Stanford study actually be showing that there is a near 0% incidence of COVID-19 in SCC?  (modulo the comments about self-selection, etc.)  Presumably, it would show some upper bound on the infection rate rather than just showing 0%.


I wonder if Stanford warned these individuals of the (low, medium, high) likelihood that their positive test could be a false positive.  I expect they warned that having antibodies didn't necessarily mean immunity.   I also kinda wonder why someone who tested positive hasn't identified themselves to the media and talked about the process and what it means to them.