WASHINGTON - The true number of COVID-19 cases in the United States may be 6 to 24 times higher than reported, according to a new study published Tuesday.

In the cross-sectional study of 16,025 residual clinical specimens, the US Centers for Disease Control and Prevention (CDC) estimated the proportion of persons with detectable SARS-CoV-2 antibodies ranged from 1 percent in the San Francisco Bay area to 6.9 percent in New York City.

The study performed serologic testing on a convenience sample of residual sera obtained from persons of all ages. The serum was collected from March 23 through May 12, for routine clinical testing by two commercial laboratory companies.

"Our results for each site suggest that the number of infections was much greater than the number of reported cases throughout the study period," said the study, published in JAMA Internal Medicine.

For most sites, it is likely that greater than 10 times more SARS-CoV-2 infections occurred than the number of reported COVID-19 cases. Most persons in each site likely had no detectable SARS-CoV-2 antibodies, according to the study.

Six to 24 times more infections were estimated per site with seroprevalence than with COVID-19 case report data, the study found.