Rapid COVID-19 tests show better than expected results in large Baltimore study

Those rapid COVID-19 tests actually do work pretty well, even if people don’t have symptoms, according to a large new study conducted in Baltimore.

Polymerase chain reaction, or PCR, tests are the gold standard for detecting COVID-19, certain to find the disease caused by the coronavirus. But rapid antigen tests, which people can now buy in a box for about $24 and conduct themselves, are becoming more common for their convenience as supplies begin to increase.


Researchers from Johns Hopkins Medicine and the University of Maryland Medical System partnered with others to make sure the rapid tests were effective.

Other studies have shown they have value, but this study may provide some heft to those findings because it’s thought to be the largest of its kind. They also said the results should influence policymakers considering ramping up their distribution as supplies are becoming more plentiful after months of slow production.


Some jurisdictions such as Baltimore City and Anne Arundel County already have begun handing them out to the public through libraries and other public places.

The study involved about 6,000 people who came for coronavirus testing to the state field hospital set up at the Baltimore Convention Center, which has since closed and moved to State Center to the north in the city.

“We found that the virus was accurately detected by the rapid antigen test in 87% of patients with COVID-19 symptoms and in 71% of those who were asymptomatic — rates that surprised us because they were so high,” said Dr. Zishan Siddiqui, the study’s lead author and an assistant professor at the Johns Hopkins University School of Medicine, in a statement.

“This is a significant finding because the rapid test offers a number of advantages over the PCR test, including time savings, both in sampling and processing; cost savings; and most importantly, ease of distribution and application — basically anywhere — which can help overcome COVID testing disparities in medically underserved communities.”

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The research was conducted by Johns Hopkins Medicine, the University of Maryland Medical Center, the University of Maryland School of Medicine and others. The Hopkins and Maryland medical systems help run the field hospital for the Maryland Department of Health.

The study was posted online Dec. 1 in the American Society for Microbiology journal Microbiology Spectrum.

For PCR tests, a patient sample containing genetic material, such as a nasal swab or saliva, is taken and examined to see if it contains COVID-19. The process can take one to three days in a lab, such as those operated by the state health department, universities or commercial outfits.

An antigen test uses lab-produced antibodies to latch onto COVID-19 proteins in the sample. They are prepackaged, easy to use by residents on themselves and provide results in about 15 minutes.


For the study, the participants were screened for COVID exposure and symptoms and then given a PCR test and the BinaxNOW COVID-19 Antigen Test made by Abbott Laboratories.

“What we determined was that while the PCR test may be a better test from a clinical perspective — as it’s basically 100% accurate at detecting SARS-CoV-2 — the rapid antigen test appears to be better from a public health standpoint because of its ease of use, and the fact that it proved to have sufficient accuracy, specificity and reliability for detecting the coronavirus in a high-volume setting,” said Dr. James Ficke, the study’s senior author and a professor of orthopedic surgery at the Johns Hopkins University School of Medicine, who also was a co-director of the field hospital.

The researchers are looking now at how well the rapid tests work in kids, with data collected on about 1,000 children so far. Results are expected in early 2022. They also plan to look specifically at the tests on the market for home use.