Forty percent of US Covid-19 tests come back too late to be clinically meaningful, data shows

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In early July, Shannon Mayer began to feel a sudden tightness in her chest.“The next day it was really hard to breathe,” the 31-year-old Chicago resident told CNBC. ” I was afraid. ”

Mayer has asthma, but says she hasn’t had a problem with it in years. She therefore decided to take a test for Covid-19. The results, she was told, would take five to ten days and she was tasked with quarantining her while she waited. After a week, the results still had not been returned. And Mayer was already feeling better and suspected she wasn’t infected, so she stopped the quarantine.

“If I had stuck with this I would have been home for three weeks,” she said. She was tested on July 1 and her results did not come back until July 24. Fortunately, she was negative. May is not alone. Bethany Silva, who lives in New York City, reported a 13-day wait for her results. For Lisa Miller, in New Jersey, it was a week.

Health experts say two days or less is optimal for returning Covid-19 test results to make them useful in stopping transmission. If test results take longer than three days, people are unlikely to quarantine themselves, and it can be difficult to get in touch with people they interact with during that time – potentially spreading the virus.

“It’s really clear that if the tests take longer than 48 hours, you’ve lost the contact tracing window,” Dr. Ashish Jha, professor of global health at Harvard University, said in an interview. “I think basically, beyond 72 hours, the test is almost useless. ”

A survey conducted by CNBC in partnership with Dynata, a global data and surveys company, suggests that nearly 40% of Americans had to wait more than three days for their results, rendering them – by Jha’s definition – unnecessary.

This is certainly how Mayer felt.“The point is if I have it before it’s over,” Mayer said. “So that completely defeated the goal. ”

Results varied from state to state. Some, like Massachusetts and South Dakota, had average delays of just over two days. Others, like Arizona and West Virginia, were closer to four and a half days, on average. The average test turnaround time in Indiana was more than five days.

Jha said the variation was evidence of a fragmented testing strategy in the United States

“It would take a national testing strategy to make sure that if there is excess capacity in Massachusetts but long lines in Florida, Massachusetts could help Florida,” Jha said. “For the most part, we haven’t had a national testing strategy. The White House strategy has been for each state to figure this out for themselves. ”

Even national labs struggled to keep up with demand when cases spiked in the Sunbelt, with Quest Diagnostics saying in mid-July that its turnaround times were over a week for non-priority patients. He has since said that this is increased capacity and results now take an average of two to three days.

Admiral Brett Giroir, the Trump administration’s Covid-19 testing czar, told NBC’s Andrea Mitchell this week that the results that take seven to 14 days are outliers.

“In general, if you need a test – you fall into the categories of needing a test, even for public health screening – you will get that result within 48-36 hours,” he said. he declares. Not everyone needs testing, Giroir said, and the national testing approach is “strategic testing, not shotgun testing,” which he says has reversed outbreaks in that region.

Indeed, daily new cases are down 44% in Florida from a peak in mid-July, while they are down 73% in Arizona, both on an average of seven days, according to the Covid Tracking Project. , a data source managed by journalists in the Atlantic.

Testing in both states is also down, by 42% in Florida and 41% in Arizona. The net result in Florida is that the positivity rate – the percentage of all tests that turn out positive – has remained around 18% since early July. This could mean that while the reported cases have declined, the actual prevalence of the virus has not declined. In Texas, testing has halved, raising questions about whether cases are really declining as much as the numbers indicate, or whether the decrease in testing obscures the real picture.

“It makes reviewing case denials much more difficult to interpret,” Jha said. “If the cases are down 30% but testing is down 30%, what happens with the cases? Is it more, is it less, is it about the same? And we all make assumptions. ”

Overall, data from Dynata shows test turnaround times in the United States have declined since March, from over four days on average to just under three and a half days.

This timing is even longer than Jha and others say it helps.

“The fact that six, seven months after the start of a pandemic, we can’t do a simple diagnostic test is amazing,” he said. “The rest of the world looks at us primarily with a state of disbelief that America cannot perform simple lab tests on an infectious disease that we have known for seven months. ”

The survey was conducted in collaboration with Dynata, a global data and survey company through a first-party online panel from July 30 to August 10. The sample included 9,444 adults in the United States, with about 200 respondents from each state, plus the District of Columbia, although some of the smaller states had fewer respondents. The data has been weighted to correct for known demographic differences. The weighted margin of error is plus or minus 1% at the national level.

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