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As the Omicron variant has swept across the U.S., now blamed for more than 98% of COVID-19 infections, the demand for testing at labs has skyrocketed — especially since home antigen tests are scarce.
On the rise, too, are complaints from test takers, who echo this anxious question:
What's taking so long for results?
Promised turnaround times of 24 to 48 hours are stretching to several days, as people wonder if they should isolate or carry on with their regular schedule.
The increased volume is a major reason, of course, but not the only one.
"You'd be surprised by what the time delays are," says Dan Milner, MD, chief medical officer for the American Society for Clinical Pathology, an organization for lab professionals.
The journey of the nasal swab — from the collection point to the test results arriving by text or email — is more involved and complicated than most people realize, Milner and other experts say. The many steps along the way, as well as staffing and other issues, including outbreaks of COVID-19 among lab staff, can delay the turnaround time for results.
First, the Volume Issue
National statistics as well as daily tallies from individual labs reflect the boom in test requests.
On Jan. 11, the average for COVID-19 tests in the U.S. reached nearly 2 million a day, an increase of 43% over a 14-day period.
By Jan. 12, Quest Diagnostics, a clinical laboratory with more than 2,000 U.S. patient locations, had logged 67.6 million COVID tests since they launched the service in 2020. That was an increase of about 3 million since Dec. 21, when their total was 64.7 million.
At the UCLA Clinical Microbiology Lab, more than 2,000 COVID tests are processed daily now, compared to 700 or 800 a month ago, says Omai B. Garner, PhD, director of clinical microbiology for the UCLA Health System. And he does not think demand has peaked.
In Tucson, AZ, at Paradigm Site Services, which contracts with local governments, businesses, and others to provide testing, 4,000 tests a day are done, compared to a daily tally of 1,000 in early November, says Steven Kelly, CEO.
Beyond volume, there are other barriers that thwart the intended turnaround time.
Swab Collection, Pickup, Transport
"People misunderstand the entire process," Garner says. One big misconception is that the swab is analyzed right at the point of collection. That's usually not true — with some rapid (and pricey) PCR test sites sometimes the exception.
Once the nasal collection is done, the specimen is sealed in a tube, then sent to a lab. It might be taken by courier to a local nearby lab, or it may be shipped much farther away, especially if it’s collected in a rural area.
"Someone could be swabbed and the swab needs to go out of state," Garner says.
And even a swab that's transported by courier to a local testing lab could take longer than expected, if traffic is heavy or the weather turns bad.
En route, temperature control is important, Kelly of Paradigm says. "Samples have to be stored at the right temperatures." Couriers often store the specimens in coolers to transport them.
Arrival at the Lab
Once the swab arrives at the lab, the samples have to be logged in.
Next, how quickly it gets tested depends on the volume of tests received at the same time -- and what the lab capacity is, taking into account staff and equipment to analyze the specimens.
Lab staffing is another factor. As the demand for tests has increased, laboratories are having a hard time adding enough staff. Requirements differ from state to state, Garner says, but those analyzing the tests must be clinical lab scientists with training and experience. And like other businesses, laboratories are dealing with employees who contract COVID-19 and must leave work to isolate.
Potential lab employees must also cope well in a high-pressure situation, says Kelly. His company has hired 30 more workers in the past 3 weeks, bringing the total to 160. Some work 7 days a week.
Testing equipment — or the lack of it — can also slow down the process.
While Garner says he's often asked if fake testing labs are popping up, he says he is not aware of any. And it's easy enough to check a lab's credentials.
Legitimate labs are certified under CLIA -- the Clinical Laboratory Improvement Amendments of 1988. Under CLIA, federal standards apply to all U.S. facilities or sites that test human specimens to assess health or to diagnose, prevent, or treat disease. The CDC has a CLIA Laboratory Search Tool to look up a lab by name to check its certification.
States may also provide information on certification and other testing details. For instance, California's COVID-19 Testing Task Force publishes its lab list, detailing locations, number of tests done weekly, and average turnaround times.
Analysis at the Lab
Labs do two types of tests to detect COVID-19. Antigen tests detect certain proteins in the virus.
"Lab-based antigen tests are not that much different" from the rapid home tests, Milner says. There is a control line and a test line used to detect the virus.
The PCR (polymerase chain reaction) tests detect genetic material of the virus.
"RNA gets extracted from the sample and is purified via our extraction instrument," says Mariah Corbit, compliance manager at Paradigm Laboratories.
Special chemicals and enzymes are added. A PCR machine called a thermal cycler performs a series of heating and cooling steps to analyze the specimen. The PCR technology allows scientists to amplify small amounts of the RNA from the specimens into DNA, which replicates until any virus present is detected.
One of the chemicals produces a fluorescent light if the virus is in the sample. That signal is detected by the PCR machine.
The PCR test can also provide an idea of how much virus the person has, says Chris Johnson, MD, medical director of Paradigm Site Services.
Once the analysis begins, it's possible to estimate how long results take, Milner says.
The longest analysis is for the PCR test, which varies from lab to lab but often requires about 1.5 to 2 hours, he says. The antigen test analysis ''takes 20 minutes at the most,'' Milner says.
In the case of the rapid PCR tests, which promise results in 1-2 hours or even less but can cost $300, the processing time may be changed to get results faster, Milner says. And in general, a positive result shows up faster than a negative. "If you are reading it in real time, you can get a positive result in 20-30 minutes and report it out."
Facilities offering the rapid tests may be doing only COVID testing and may be processing the tests at the same site, Milner says, allowing for the faster turnaround. "If they are CLIA-certified, the quality of that test should be OK,'' he says.
A lab's definition of turnaround time for the non-rapid tests may differ from that of the person awaiting the result. Quest Diagnostics, for instance, says its turnaround timeline starts at the end of the day on which the specimen is collected and ends at the end of the day on which results are reported.
A positive result is reported as such, as is a negative. "There is no confirmation testing," Garner says. "This is why labs need to run reliable tests."
But the test is repeated if the original result isn’t conclusive, Garner says. And if it's not conclusive a second time? "We release it as indeterminate," and another test can be ordered.
Once finalized, the results are sent via text or email.
With no slowdown in demand expected in the near future, long-term fixes are needed.
"From a lab standpoint, we are all so frustrated we don't have the infrastructure and capacity to meet the need," Garner says. "In general, we have not built the testing infrastructure needed to fight the pandemic."
At the beginning of the pandemic, he says, when demand first ramped up, "we should have looked on it as a need to build the infrastructure."
Meanwhile, lab directors know how important timely results are, but won't sacrifice speed for accuracy. "We want to make sure it's done right," Kelly says.
Omai B. Garner, PhD, associate clinical professor and director of clinical microbiology, UCLA Health System.
Steven Kelly, CEO, Paradigm Site Services, Tucson, AZ.
Chris Johnson, MD, medical director, Paradigm Site Services, Tucson, AZ.
Mariah Corbit, compliance manager, Paradigm Laboratories, Tucson, AZ.
Dan Milner, MD, chief medical officer, American Society for Clinical Pathology.
Mayo Clinic: "COVID-19 diagnostic testing."
Quest Diagnostics: "Media Statement about COVID-19 Testing."
The New York Times: "Coronavirus in the U.S.: Latest Map and Case Count."
Cleveland Clinic: "COVID-19 and PCR Testing."
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Cite this: Why Your COVID Test Results Take That Long - Medscape - Jan 14, 2022.