[2006alum]

A new serology study from Los Angeles county gave roughly the same results as the Stanford test: http://publichealth.lacounty.gov/phcommo...?prid=2328  They estimate ~400,000 infected in LA county.

I haven't been able to find a final report, but people on the internet (reliable, I know) are saying it's the same test they used at Stanford, so that's still a problem. The sampling was better than Stanford but there is still going to be quite a bit of self-selection until you literally force people to take the test (China probably has a leg up over the US in this department). 

Anyway, I'll withhold final judgment until I see a report.

Indeed. I'm pretty frustrated that the recruitment techniques/scripts are "proprietary" (so the public doesn't get to see them), they have not released the raw data, and they used Chinese-made tests that were never validated in China and were later banned for export from China, per NBC news:

But some COVID-19 antibody tests, including those being used by public health departments in Denver and Los Angeles and provided to urgent care centers in Maryland and North Carolina, were supplied by Chinese manufacturers that are not approved by China's Center for Medical Device Evaluation, a unit of the National Medical Product Administration, or NMPA, the country's equivalent of the U.S. Food and Drug Administration, NBC News has found.

Two U.S. companies — Premier Biotech of Minneapolis and Aytu Bioscience of Colorado — have been distributing the tests from unapproved Chinese manufacturers, according to health officials, FDA filings and a spokesman for one of the Chinese manufacturers. Many of the unapproved tests appear to have been shipped to the U.S. after the FDA relaxed its guidelines for tests in mid-March and before the Chinese government banned their export just over two weeks later.

From USC Q&A about the Study:

How people were selected for this study?
Participants for the USC-L.A. County study were recruited by the market services firm LRW Group using a large proprietary database that ensures factors such as age, race and sex are part of the random selection. For the first testing that took place on April 10 and 11, USC and the L.A. County Department of Public Health identified six sites for drive-thru testing. Our plan moving forward is to test a different group of 1,000 randomly selected people every several weeks.

How reliable are the antibody tests?
Premier Biotech, the manufacturer of the test that USC and L.A. County are using, tested blood from COVID-19-positive patients with a 90 to 95% accuracy rate. The company also tested 371 COVID-19-negative patients, with only two false positives. We also validated these tests in a small sample at a lab at Stanford University. When we do our analysis, we will also adjust for false positives and false negatives.

Without seeing the underlying dataset, it's really hard to determine whether they have similar issues with their confidence intervals including the possibility that all the positive are false positives. It's also odd that the reports show that 6% of men vs. 2% of women tested positive, and 7% of African Americans vs. 2.5% of Latinos. That is a suspiciously wide variation.

[2006alum]

A new serology study from Los Angeles county gave roughly the same results as the Stanford test: http://publichealth.lacounty.gov/phcommo...?prid=2328  They estimate ~400,000 infected in LA county.

I haven't been able to find a final report, but people on the internet (reliable, I know) are saying it's the same test they used at Stanford, so that's still a problem. The sampling was better than Stanford but there is still going to be quite a bit of self-selection until you literally force people to take the test (China probably has a leg up over the US in this department). 

Anyway, I'll withhold final judgment until I see a report.

Indeed. I'm pretty frustrated that the recruitment techniques/scripts are "proprietary" (so the public doesn't get to see them), they have not released the raw data, and they used Chinese-made tests that were never validated in China and were later banned for export from China, per NBC news:

But some COVID-19 antibody tests, including those being used by public health departments in Denver and Los Angeles and provided to urgent care centers in Maryland and North Carolina, were supplied by Chinese manufacturers that are not approved by China's Center for Medical Device Evaluation, a unit of the National Medical Product Administration, or NMPA, the country's equivalent of the U.S. Food and Drug Administration, NBC News has found.

Two U.S. companies — Premier Biotech of Minneapolis and Aytu Bioscience of Colorado — have been distributing the tests from unapproved Chinese manufacturers, according to health officials, FDA filings and a spokesman for one of the Chinese manufacturers. Many of the unapproved tests appear to have been shipped to the U.S. after the FDA relaxed its guidelines for tests in mid-March and before the Chinese government banned their export just over two weeks later.

From USC Q&A about the Study:

How people were selected for this study?
Participants for the USC-L.A. County study were recruited by the market services firm LRW Group using a large proprietary database that ensures factors such as age, race and sex are part of the random selection. For the first testing that took place on April 10 and 11, USC and the L.A. County Department of Public Health identified six sites for drive-thru testing. Our plan moving forward is to test a different group of 1,000 randomly selected people every several weeks.

How reliable are the antibody tests?
Premier Biotech, the manufacturer of the test that USC and L.A. County are using, tested blood from COVID-19-positive patients with a 90 to 95% accuracy rate. The company also tested 371 COVID-19-negative patients, with only two false positives. We also validated these tests in a small sample at a lab at Stanford University. When we do our analysis, we will also adjust for false positives and false negatives.

Without seeing the underlying dataset, it's really hard to determine whether they have similar issues with their confidence intervals including the possibility that all the positive are false positives. It's also odd that the reports show that 6% of men vs. 2% of women tested positive, and 7% of African Americans vs. 2.5% of Latinos. That is a suspiciously wide variation.