BOSTON — Those long lines to get tested for Covid-19 are having a spillover effect on the labs processing those millions of samples.
Quest Diagnostics, which handles about one fifth of the nation’s Covid-19 samples, reported a 50% rise in volume in the last eight weeks, with the average nationwide positivity rate climbing above 10%. Adding to the company’s stress: a shortage of standard lab supplies.
That’s led to a rise in average national turnaround time to beyond the two days seen since August.
In Massachusetts, the average 14-day turnaround time for sample reporting to the Department of Public Health has also climbed from 1.79 days earlier this month to 1.92 days most recently.
“The fact that there’s a spike in demand for testing is directly correlated to both the rise in cases themselves and also concern that people might have that they be infected,” said Stephen Kissler, PhD of the Harvard School of Public Health. “As well as, of course the coming holidays where people may be wanting to get tested to see whether or not they’re infectious and bringing infection to their families. All of these things are driving this increase in testing that you’re seeing.”
Kissler said the testing delays may be averaging two days -- but not everywhere.
“There’s of course a lot of variation across the country that depends a lot on where the laboratories are that run the tests and the number of tests that are available in any given location,” said Kissler.
Waiting an excessive amount of time for test results is more than an inconvenience when it comes to Covid-19. It has real public health consequences, according to Kissler.
“If it ranges past three or four days then the information you get back is less and less meaningful. And so that’s the real concern,” said Kissler. “We would like to be able to turn around these tests as quickly as possible but that’s becoming more and more challenging.”
One area testing delays can have a serious impact is on contact tracing, considered a key way to help contain viral transmission.
“If contact tracing doesn’t actually initiate until well after you actually took the test then you can’t adequately capture your own contacts and then it’s a lot more difficult to limit spread,” said Kissler.
Karl Minges, PhD, MPH, chair of the Health Administration and Policy department at the University of New Haven in Connecticut, said those contemplating getting a test just to travel for Thanksgiving might think about who they’re displacing.
“Do you need a test? Yeah, if you were exposed you need a test,” Minges said. “Do you want a test because you want to be sure of your results? I understand why people want that. But at the end of the day, given the surge, it’s about taking priority.”
It’s also about common sense since information from any test is a snapshot in time that won’t guarantee non-infectiousness the following week.
Kissler has studied the decline in accuracy of Covid tests over time.
“It turns out it can decline very quickly,” he said.
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