LOS ANGELES, April 20 (Reuters) - Some 4.1% of adults tested positive for coronavirus antibodies in a study of Los Angeles County residents, health officials said on Monday, suggesting the rate of infection may be 40 times higher than the number of confirmed cases.

Reuters: The serology tests, conducted by University of Southern California researchers on 863 people, indicate the death rate from the COVID-19 could be lower than previously thought but also that the illness may be being spread more widely by people without symptoms

Reuters: "We haven't known the true extent of COVID-19 infections in our community because we have only tested people with symptoms and the availability of tests has been limited," Neeraj Sood, a professor of public policy at USC and lead researcher on the study.

Reuters: "The estimates also suggest that we might have to recalibrate disease prediction models and rethink public health strategies," Sood said.

Reuters: The Los Angeles County results were announced as antibody tests come under increasing scrutiny over a high number of false positives reported in the kits.

Reuters: A similar study conducted in Santa Clara County last week by a Stanford University researcher has been criticized over its methodology and sample size.

Reuters: The antibody tests, using decades-old ELISA technology, do not always pick up early-stage infections but show whether a person had the virus in the past, even if the person was asymptomatic.

Reuters: In comparison, the so called RT-PCR-technology swab tests used at drive-through stations and clinics across the country determine whether a person has the virus at that moment by looking for it in nose or throat secretions.

Reuters: Both tests are seen as critical in the coronavirus fight, but antibody tests are seen as a relatively cheap, fast means to sort populations into risk groups and measure virus spread.

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