At-home Covid testing raises questions about the accurate counting of cases

At-home Covid testing raises questions about the accurate counting of cases


Millions of rapid home Covid tests are flying off pharmacy shelves across the country, allowing Americans to read immediately, albeit sometimes imperfectly, whether they are infected with the coronavirus.

However, the results are rarely reported to public health authorities, exacerbating the long-standing challenges of maintaining an accurate count of cases at a time when the number of infections due to the Omicron variant is rising.

At least the widespread availability of home tests is devastating to the accuracy of official positivity rates and case numbers. On the flip side, it’s a factor that leads some public health experts to ask a question that would previously have been unthinkable: are coronavirus case counts useful, and if not, should they continue?

“Our entire approach to the pandemic has been case-based surveillance: we have to count every case, and that’s just not accurate anymore,” said Dr. Marcus Plescia, Chief Medical Officer for the Association of State and Territorial Health Officials, a national not-for-profit organization representing public health authorities in the United States. “It just becomes a time when we have to think about doing things differently.”

There is no comprehensive data on how many rapid tests are used each day, but experts say it is most likely far higher than the number of polymerase chain reaction or PCR tests that are done in a laboratory and that take longer to get results that are reported publicly as aggregated sums.

At least one home testing company has implemented a system to report the results directly to health authorities. And some local health departments have systems in place that people can use to report rapid test results at home. But with such a voluntary system, it is possible that millions of tests per day will go unreported, estimates Mara Aspinall, an expert in biomedical diagnostics at Arizona State University who also sits on the board of OraSure, which performs rapid Covid tests.

“We certainly don’t want to discourage testing, but at the same time we mustn’t leave the health authorities blind,” said Ms. Aspinall. “They rely on this information to take proactive and reactive precautions. It’s a very fine balance. “

The rapid rise in home tests could be a turning point in a conversation that began months ago for public health experts. It is about the possibility of moving to less frequent case reports or a “sentry surveillance system” such as is currently used by health authorities to track other diseases such as the flu, which is based on a network of health centers, the incidents of the virus. The total number of cases is extrapolated based on these case numbers.

Concerns have also been expressed about the accuracy of the tests themselves. The Food and Drug Administration said Tuesday that antigen tests detect the Omicron variant, but not as effectively as other variants.

Throughout the pandemic, daily case numbers played a central role in shaping policy responses to the pandemic. Cities have introduced masking requirements and closed schools or businesses in response to positivity rates based on daily case numbers. In New York City, the public school system closed at a time when the positivity rate reached 3 percent.

Public health officials, as well as news outlets like the New York Times, continue to use daily case counts to paint an up-to-date picture of the pandemic.

However, due to limited access to testing and the prevalence of asymptomatic cases, case numbers have long been considered artificially low. And putting these numbers together is a labor-intensive task for the already strained health authorities.

As a result, many states began moving from daily case counts to less frequent weekly reporting during the summer as cases declined. Some returned to more frequent reports as the number of cases rose again. But with the Omicron variant fueling a rapid surge in positive cases, states are finding they can’t keep up. And with so many more cases that haven’t been reported through home testing anyway, there’s little incentive to try.

Dr. Marcelle Layton, chief medical officer at the Council of State and Territorial Epidemiologists, said her organization had spoken to its members about moving away from the daily case count, with many still reporting daily eager to see the changeover in the coming one Months. Her organization was also in contact with the Centers for Disease Control and Prevention about possible guidelines that would instruct states to restrict daily case reporting. A CDC spokesman said the agency has no plans to change state reporting guidelines.

Tennessee announced last week that it would be reporting weekly Covid case data that is consistent with other infectious diseases. Home testing and delays in reporting from health facilities have made the state’s daily case numbers inaccurate, said state health commissioner Dr. Lisa Piercey, at a press conference last week.

“This is not a sustainable way of doing this permanently,” she said. She added, “Reporting numbers on a daily basis really isn’t that relevant anymore. It’s relevant to trends, but the actual number isn’t that accurate if you don’t know what you don’t know. “

The state will also begin reporting its test positive rate based solely on PCR testing, rather than the limited number of rapid tests that it receives reports.

“Everyone knew that time was coming,” said Dr. Layton of the Council of Epidemiologists, adding that the postponement was part of a move closer to Covid-19 as an endemic disease that the country would have to live with indefinitely, much like flu.

Other experts say that while daily reporting is not essential in the long term, the rapid spread of Omicron requires health officials to keep daily reporting up.

“The reason we came here is because the virus moved so quickly – if you are five days behind, you are already in the infection phase for many people,” said Stefanie Friedhoff, professor at the School of Brown University Public Health. “As long as we are in this Omicron wave, we have to understand our daily numbers as well as possible.”

Health officials should report case numbers on a daily basis, she argued, but the limits of the data available should be clearer, she said.

Realizing the limits of the daily number of cases, local health officials have turned to a variety of other sources to track the spread of the virus, such as hospitalization trends and direct reports from community leaders.

Dr. Jessica Guernsey, director of health for the Multnomah County’s Public Health Department in Oregon, which covers the Portland area, said these other metrics have become more useful than the focus on tracking the total number of cases, given home testing and the rapid spread of Omicron.

“Given the situation we are facing with something as aggressive as Omicron, testing, isolation, and contact tracing become much less relevant,” said Dr. Guernsey. “At some point this kind of constant drum roll helps us understand that there is a lot of Covid out there, not much better.”

Nonetheless, masking Covid cases through home testing poses some challenges for local health officials, said Dr. Rachel Rubin, senior physician for the Cook County Department of Public Health in Illinois. Failure to report positive test results from infected people to schools or nursing homes will hamper the county’s ability to advise those facilities on isolation procedures or identify other cases associated with the cluster.

“It’s like a double-edged sword,” said Dr. Ruby. On the one hand, the rise in home tests is a positive development that enables people to isolate themselves if necessary. On the other hand, it leaves health authorities in the dark. “I think we’re just picking the tip of the iceberg of positive tests,” she said.



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Rachel Meadows

Rachel Meadows

Trending topics news writer who enjoys cooking, walking her dog and travel.

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