FRIDAY, May 22, 2020 (HealthDay News) -- In recent serologic tests, the weighted prevalence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies was 4.65 percent among adult residents of Los Angeles County, California, after adjustment for test sensitivity and specificity, according to a research letter published online May 18 in the Journal of the American Medical Association.
Neeraj Sood, Ph.D., from the University of Southern California in Los Angeles, and colleagues tested for SARS-CoV-2-specific antibodies in a sample of adult residents of Los Angeles County, California, within a 15-mile radius of the testing site. Participants were offered testing on April 10 and 11, 2020, at six study sites or in-home testing on April 13 and 14, 2020. The data were used to estimate the population prevalence of SARS-CoV-2 antibodies.
The researchers found that 865 of 1,952 individuals invited to participate in antibody testing were tested. Two test results were inconclusive and removed from the analysis. Of the 863 adults included, 35 (4.06 percent) tested positive; the weighted proportion of participants that tested positive was 4.31 percent. The unweighted and weighted prevalence of SARS-CoV-2 antibodies was 4.34 and 4.65 percent, respectively, after adjustment for test sensitivity and specificity.
"The estimate implies that approximately 367,000 adults had SARS-CoV-2 antibodies, which is substantially greater than the 8,430 cumulative number of confirmed infections in the county on April 10," the authors write. "Fatality rates based on confirmed cases may be higher than rates based on number of infections. In addition, contact tracing methods to limit the spread of infection will face considerable challenges."
One author disclosed financial ties to the medical insurance industry.