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Why your COVID test results take so long


January 14, 2022 – As the Omicron variant swept across the United States, now responsible for more than 98% of COVID-19 infections, demand for testing in labs has skyrocketed – especially as testing for Home antigens are rare.

Increasingly, complaints from candidates, which echo this anxiety-provoking question:

What takes so long to get results?

Promised turnaround times of 24 to 48 hours stretch into days as people debate whether to self-isolate or continue with their regular schedule.

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

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

The nasal swab journey — from point of collection to test results arriving via text or email — is more involved 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 COVID-19 outbreaks among lab staff, can delay the time to get results.

First, the problem of volume

National statistics as well as daily tallies from individual labs reflect the surge in demand for testing.

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

As of January 12, Quest Diagnostics, a clinical laboratory with more than 2,000 patient locations in the United States, had logged 67.6 million COVID tests since the service launched in 2020. This represents an increase of approximately 3 million since on December 21, when their total was 64.7 million.

At UCLA’s Clinical Microbiology Lab, more than 2,000 COVID tests are now being processed daily, up from 700 or 800 a month ago, says Omai B. Garner, PhD, director of clinical microbiology for the UCLA Health System. the UCLA. And he doesn’t 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 being performed, up from a daily tally of 1,000 in early November, Steven says Kelly, CEO.

Beyond volume, there are other hurdles that thwart the expected turnaround time.

Collection of swabs, collection, transport

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

After the nasal swab is taken, the specimen is sealed in a tube and then sent to a lab. It can be couriered to a nearby local laboratory, or it can be shipped much further, especially if collected in a rural area.

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

And even a swab couriered to a local testing lab can take longer than expected, if traffic is heavy or the weather turns bad.

En route, temperature control is important, says Kelly of Paradigm. “The samples must be stored at the correct temperature.” Couriers often store specimens in coolers for transport.

Arrival at the Lab

Once the swab arrives at the lab, the samples must be registered.

Then the speed with which it is tested depends on the volume of tests received at the same time – and the capacity of the laboratory, taking into account the personnel and the equipment to analyze the samples.

Another factor is the staffing of the laboratory. As demand for tests has increased, labs are struggling to recruit enough staff. Requirements differ from state to state, Garner says, but those analyzing the tests must be clinical laboratory scientists with training and experience. And like other businesses, labs are dealing with employees who contract COVID-19 and have to leave work to self-isolate.

Potential lab workers also need to handle a high-pressure situation well, Kelly says. His company has hired 30 more workers in the past 3 weeks, bringing the total to 160. Some are working 7 days a week.

Testing 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 them. And it’s pretty easy 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 US facilities or sites that test human specimens to assess health or to diagnose, prevent or treat disease. The CDC has a CLIA lab search tool to search for a lab by name to verify its certification.

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

Laboratory analysis

Laboratories perform two types of tests to detect COVID-19. Antigen tests detect certain proteins of the virus.

“Antigen tests in the lab are not that different” from rapid home tests, says Milner. There is a control line and a test line used to detect the virus.

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

“The RNA is extracted from the sample and is purified through our extraction instrument,” explains Mariah Corbit, chief compliance officer 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 any virus present is detected.

One of the chemicals produces fluorescent light if the virus is in the sample. This signal is detected by the PCR machine.

The PCR test can also give an idea of ​​how much virus the person has, says Chris Johnson, MD, chief medical officer of Paradigm Site Services.

Once the scan begins, it’s possible to estimate how long the results will last, 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. The analysis of the antigen test “takes a maximum of 20 minutes”, explains Milner.

In the case of rapid PCR tests, which promise results in 1 to 2 hours or even less but can cost $300, the processing time can be changed to get results faster, Milner says. And in general, a positive result appears faster than a negative. “If you read it in real time, you can get a positive result in 20-30 minutes and report it.”

Facilities offering the rapid tests can only do COVID tests and can process the tests at the same site, Milner says, allowing for faster turnaround. “If they’re CLIA certified, the quality of that test should be decent,” he says.

A lab’s definition of turnaround time for non-rapid tests may differ from that of the person waiting for the result. Quest Diagnostics, for example, indicates that its runtime begins at end of the day from which the specimen is taken and ends at the end of the day on which the results are reported.

Verification of results

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

But the test is repeated if the initial result is inconclusive, Garner says. And if it is not conclusive a second time? “We publish it as indeterminate”, and another test can be ordered.

Once finalized, the results are sent by SMS or e-mail.

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 need,” says Garner. “In general, we haven’t built the necessary testing infrastructure to fight the pandemic.”

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

Meanwhile, lab managers know how important timely results are, but won’t sacrifice speed for accuracy. “We want to make sure everything is done right,” Kelly says.


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