As the list of available antibody tests for the COVID-19 virus soars, scientists and the FDA are investigating their accuracy and effectiveness. Only 12 have received FDA authorization for emergency use. Assistant bioengineering professor Patrick Hsu and UCSF microbiology and immunology professor Alex Marson are both working on the Berkeley-UCSF Innovative Genomics Institute's effort to study more than 100 antibody test kits for their effectiveness. According to this reporter: "To assess their ability to identify antibodies against SARS-CoV-2, the team used plasma or serum samples from three groups: 80 people who had shown symptoms of COVID-19 and had tested positive using a PCR-based screen, 52 who had a respiratory infection but were found to be infected with another virus or had tested negative on a PCR test for SARS-CoV-2, and 108 blood donors whose samples were drawn in 2018 or earlier, before the pandemic began. ... Their assessment found that the ability to detect antibodies in people who had tested positive for the virus increased over time, rising to 81–100 percent when more than 20 days had elapsed since symptoms began, depending on the product. One of the members of the team, Patrick Hsu ... notes that this finding highlights why longitudinal antibody testing is important, given that a negative result may mean a person had been exposed to the virus but hadn't yet developed a detectable level of antibodies. On the specificity side, the proportion of false positives found in the pre–COVID-19 samples ranged from 0–16 percent. The agreement between the findings of LFAs and ELISAs ranged from 75–94 percent. The team posted its results as a preprint on the project website on April 24. Alex Marson ... cautions that some numbers, especially for tests' ability to detect antibodies in positive cases, may be revised as his team continues to analyze the data."