Jan. 14, 2022 — As the Omicron variant has taken hold in the United States and is now blamed for more than 98% of COVID-19 infections, the demand for testing in laboratories has skyrocketed — especially as antigen testing for are scarce at home.

Also on the rise are complaints from test-takers repeating this anxious question:

Why does it take so long to show results?

The promised turnaround times of 24 to 48 hours are stretching to several days as people question whether to isolate or continue with their regular schedule.

The increased volume is of course a major reason, but not the only one.

“You’d be surprised at how large the time lags are,” says Dan Milner, MD, chief medical officer of the American Society for Clinical Pathology, an organization for laboratory professionals.

The nasal swab journey — from the sampling site to the test results arriving via text message or email — is more circuitous and complicated than most people realize, say Milner and other experts. The many steps along the way, as well as staffing and other issues, including outbreaks of COVID-19 among laboratory staff, can delay the turnaround time for results.

First the volume problem

National statistics and daily evaluations by individual laboratories reflect the boom in test requests.

On January 11, the average for COVID-19 tests in the US reached nearly 2 million per day, a 43% increase over a 14-day period.

As of Jan. 12, Quest Diagnostics, a clinical lab with more than 2,000 patient sites across the United States, had logged 67.6 million COVID tests since they launched the service in 2020. That was an increase of about 3 million since December 21, when their total was 64.7 million.

More than 2,000 COVID tests are now processed daily at the UCLA Clinical Microbiology Lab, compared to 700 or 800 a month ago, says Omai B. Garner, PhD, director of clinical microbiology for the UCLA Health System. And he doesn’t think demand has peaked.

In Tucson, AZ, Paradigm Site Services, which contracts with local governments, businesses and others to provide testing, is running 4,000 tests a day, down from a daily count of 1,000 in early November, says Steven Kelly, CEO.

Beyond volume, there are other obstacles that thwart the intended turnaround time.

Swab collection, collection, transport

“People misunderstand the whole process,” says Garner. A big misconception is that the swab is analyzed directly at the point of collection. This is usually not true – sometimes the exception with some fast (and expensive) PCR test sites.

Once the nasal collection is complete, the sample is sealed in a tube and then sent to a lab. It can be couriered to a local lab nearby or shipped much further afield, especially if collected in a rural area.

“Someone could be swabbed and the swab has to go out of state,” says Garner.

And even a swab that’s couriered to a local testing lab can take longer than expected in heavy traffic or inclement weather.

Temperature control is important when you’re on the move, says Paradigm’s Kelly. “Samples need to be stored at the right temperatures.” Couriers often store the samples in coolers for transport.

Arrival at the laboratory

As soon as the swab arrives at the laboratory, the samples must be registered.

Next, how quickly it’s tested will depend on the volume of tests received at one time — and lab capacity, taking into account staff and equipment to analyze the samples.

Laboratory staff is another factor. As demand for testing has increased, labs are struggling to hire enough staff. Requirements vary from state to state, Garner says, but those analyzing the tests must be clinical laboratory scientists with training and experience. And like other companies, labs are dealing with employees who contract COVID-19 and have to leave work to isolate.

Potential lab workers also need to be able to cope well in a high-pressure situation, says Kelly. His company has hired 30 more workers in the last 3 weeks, bringing the total to 160. Some work 7 days a week.

Test equipment – or lack thereof – can also slow down the process.

While Garner says he’s often asked if fake testing labs are popping up, he says he’s not aware of any. And it’s easy to verify a lab’s credentials.

Legitimate laboratories are certified under CLIA – the Clinical Laboratory Improvement Amendments of 1988. Under CLIA, federal standards apply to any US facility or location that tests human samples to assess health status or to diagnose, prevent, or treat disease. The CDC has a CLIA lab search tool that you can use to find a lab by name to verify its certification.

States can also provide information about certification and other testing details. For example, California’s COVID-19 Testing Task Force publishes its lab list detailing locations, number of tests performed weekly, and average turnaround times.

Analysis in the laboratory

Laboratories run two types of tests to detect COVID-19. Antigenic tests detect specific proteins in the virus.

“Laboratory-based antigen tests aren’t that different” from the quick home tests, says Milner. There is a control line and a test line that are used to detect the virus.

The PCR tests (polymerase chain reaction) detect genetic material of the virus.

“RNA is extracted from the sample and purified through 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 sample. PCR technology allows scientists to amplify small amounts of RNA from samples into DNA, which replicates until virus present is detected.

One of the chemicals creates a fluorescent light when the virus is in the sample. This signal is recognized by the PCR machine.

The PCR test can also give 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 the results will take, says Milner.

The longest analysis is for the PCR test, which varies from lab to lab but often takes around 1.5 to 2 hours, he says. Analyzing the antigen test “takes 20 minutes at most,” says Milner.

For the rapid PCR tests, which promise results in 1-2 hours or even less but can cost $300, the turnaround time can be modified to get results faster, Milner says. And in general, a positive result will show up faster than a negative one. “If you read it in real time, you can get a positive result in 20 to 30 minutes and report it.”

Facilities offering the rapid tests may only do COVID testing and may process the tests at the same location, Milner says, allowing for faster processing. “If they’re CLIA certified, the quality of this test should be fine,” he says.

A lab’s definition of turnaround time for the non-rapid tests may differ from that of the person waiting for the result. For example, Quest Diagnostics says its turnaround time begins at the end of the day the sample is collected and ends at the end of the day the results are reported.

review results

A positive result is reported as such, as is a negative one. “There are no confirmatory tests,” says Garner. “That’s why labs need to run reliable tests.”

But the test is repeated if the original result is inconclusive, Garner says. And if it’s inconclusive a second time? “We release it as indefinite,” and another test can be ordered.

Upon completion, results are sent via SMS or email.

Long-term solutions

With no slowdown in demand expected in the near future, long-term solutions are needed.

“From a lab perspective, we’re all so frustrated that we don’t have the infrastructure and capacity to meet the demand,” says Garner. “In general, we have not built the testing infrastructure needed to combat the pandemic.”

At the start of the pandemic, he says, when demand was first ramping up, “we should have seen it as a need to build infrastructure.”

Laboratory leaders now understand the importance of timely results, but don’t sacrifice speed for accuracy. “We want to make sure it’s done right,” says Kelly.


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