After struggling to expedite coronavirus testing, the US can now screen millions of people every day thanks to a growing range of rapid tests. However, the boom brings with it a new challenge: keeping an eye on the results.
All US test sites are required by law to report their positive and negative results to public health authorities. According to state health officials, many rapid tests go unreported, which means some new COVID-19 infections may not be counted.
And the situation could get worse, experts say. The federal government is supplying more than 100 million of the latest rapid tests to states for use in public schools, assisted living centers, and other new testing locations.
“Schools are certainly not able to report these tests,” said Dr. Jeffrey Engel of the Council of State and Territorial Epidemiologists. “If it’s finished at all, it will likely be paper based, very slow and incomplete.”
At the beginning of the outbreak, almost all US testing relied on genetic testing, which could only be developed in high-tech laboratories. Even under the best of circumstances, people had to wait around two to three days to see results. Experts pushed for more rapid on-site tests that could be done in doctors’ offices, clinics and other facilities to quickly find infected people, quarantine them and stop the spread.
Cheaper 15-minute tests that detect viral proteins called antigens on a nasal swab became available in the summer. The first versions still had to be processed with portable reading devices. Abbott Laboratories’ millions of new tests now being conducted in States are even easier to use: they’re about the size of a credit card and can be developed with a few drops of chemical solution.
Federal health officials say roughly half of the country’s daily testing capacity is now made up of rapid tests.
Large hospitals and laboratories electronically share their results with government health departments, but there is no standardized way to report the rapid tests that are often done elsewhere. And state officials have often been unable to keep track of where these tests are being sent and whether results are being reported.
In Minnesota, officials formed a special team to try to get more test data from nursing homes, schools, and other newer test sites that are only inundated with faxes and paper files.
“It’s definitely a challenge because now we have to do a lot more things manually than we do with electronic reporting,” said Kristen Ehresmann of the Minnesota Department of Health.
Even before Abbott’s latest BinaxNOW rapid tests hit the market last month, undercount was an issue.
Competitors Quidel and Becton Dickinson have together shipped well over 35 million of their own rapid tests since June. This massive influx of tests, however, has not been reflected in the national test numbers, which for months have mostly been between 750,000 and 950,000 daily tests.
In addition to capturing new cases, COVID-19 test numbers are used to calculate a key metric for the outbreak: the percentage of tests positive for COVID-19. The World Health Organization recommends that countries test enough people to reduce their percentage of positives below 5%. And the US has been largely moving around or below that rate since mid-September, a point President Donald Trump and his top aides have touted to argue the nation turned the corner in the outbreak. The number has fallen from a high of 22% in April.
However, some disease tracking specialists are skeptical. Engel said members of his group think they are not all getting results.
“So it could be a wrong conclusion,” he said.
One of the challenges to an accurate count: States have completely different approaches. Some states summarize all types of tests in a report, some do not tabulate the rapid antigen tests at all, and others do not publish their system. Because antigen tests are more prone to false negative results and sometimes require retesting, most health professionals say they should be recorded and analyzed separately. Currently, however, the vast majority of states are not and are posting the results online.
The federal government assigns the tests to states based on their population, rather than helping them develop a strategy based on the size and severity of their outbreaks.
“That’s just lazy,” said Dr. Michael Mina from Harvard University. “Most states will not have the expertise to figure out how best to use these.”
Instead, Mina said the federal government should direct the limited test supplies to key hotspots across the country to help fight infections in the hardest-hit communities. Tighter controls would also ensure that test results are reported quickly.
Gigi Gronvall, a researcher at Johns Hopkins University, agrees that health officials need to carefully consider where and when the tests should be done. Eventually, methods of tracking the tests will catch up, she said.
“I think having the tools to determine if someone is contagious is a higher priority,” she said.
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