[burger]

I guess what I'm slightly confused about with this study is that they got 50 positive results out of 3,330 tests, for a crude prevalence rate of 1.5%.

And the study design also may be somewhat unrepresentative. As they say themselves, "bias favoring those with prior COVID-19-like illnesses seeking antibody confirmation are also possible. The overall effect of such biases is hard to ascertain." And thus, they didn't try. So based on their estimated sensitivity, coupled with their demographic weighting, they drew from 50 positive results a prevalence rate as high as 4.16%.

I'd bet a large sum of money that they got an unrepresentative sample.  It just makes sense that people who would go out of their way to get blood drawn are curious about their exposure.  So their sample probably had a disproportionate number of people who either had symptoms or were exposed to the virus through family, coworkers, etc.  With only 50 positives, it wouldn't take many such people to produce a highly biased estimate.

Reports from Wuhan today are saying that 2.5% of hospital employees there were seropositive.  I have trouble imagining that there's a higher prevalence in an entire US county that has far fewer deaths per capita.  

I hope this paper doesn't get published without brobdingnagian alterations.

[burger]

I guess what I'm slightly confused about with this study is that they got 50 positive results out of 3,330 tests, for a crude prevalence rate of 1.5%.

And the study design also may be somewhat unrepresentative. As they say themselves, "bias favoring those with prior COVID-19-like illnesses seeking antibody confirmation are also possible. The overall effect of such biases is hard to ascertain." And thus, they didn't try. So based on their estimated sensitivity, coupled with their demographic weighting, they drew from 50 positive results a prevalence rate as high as 4.16%.

I'd bet a large sum of money that they got an unrepresentative sample.  It just makes sense that people who would go out of their way to get blood drawn are curious about their exposure.  So their sample probably had a disproportionate number of people who either had symptoms or were exposed to the virus through family, coworkers, etc.  With only 50 positives, it wouldn't take many such people to produce a highly biased estimate.

Reports from Wuhan today are saying that 2.5% of hospital employees there were seropositive.  I have trouble imagining that there's a higher prevalence in an entire US county that has far fewer deaths per capita.  

I hope this paper doesn't get published without brobdingnagian alterations.