Why your COVID test results take so long

January 14, 2022 – As the Omicron variant is swept across the United States, which is now blamed for more than 98% of COVID-19 infections, the demand for testing in laboratories has risen sharply – especially as antigen testing in the home is few.

Also increasing are complaints from test participants who repeat this anxious question:

What takes so long for results?

The promised treatment times of 24 to 48 hours extend to several days as people wonder whether to isolate themselves or continue with their normal schedule.

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

“You will be amazed at what the time delays are,” says Dan Milner, MD, chief physician of the American Society for Clinical Pathology, an organization for laboratory professionals.

The journey of the nose graft – from the collection point to the test results that arrive via text message 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 staff and other issues, including outbreaks of COVID-19 among laboratory staff, can delay the processing time for results.

First, the binding problem

National statistics as well as daily figures from individual laboratories reflect the boom in test requests.

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

By January 12, Quest Diagnostics, a clinical laboratory with more than 2,000 U.S. patient sites, had registered 67.6 million COVID tests since launching the service in 2020. That was an increase of about 3 million since December 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 authorities, businesses and others to provide testing, 4,000 tests are performed per day compared to a daily figure of 1,000 in early November, says Steven Kelly, CEO.

In addition to volume, there are other barriers that counteract the intended turnaround time.

Pick-up of swabs, pick-up, transport

“People misunderstand the whole process,” Garner says. A major misconception is that the swab is analyzed right at the collection site. This is usually not true – with some quick (and expensive) PCR test sites sometimes the exception.

When the nose collection is complete, the sample is sealed in a tube and then sent to a laboratory. It can be taken by courier to a local laboratory nearby, or it can be sent much further away, especially if collected in a rural area.

“Someone could be swabbed and the swab should be out of condition,” Garner says.

And even a cotton swab transported by courier to a local test lab can take longer than expected if traffic is heavy or the weather gets bad.

Along the way, temperature control is important, says Kelly from Paradigm. “Samples must be stored at the correct temperatures.” Couriers often store the samples in coolers to transport them.

Arrival at the laboratory

When the swab arrives at the laboratory, the samples must be logged.

Next, how quickly it is tested depends on the amount of tests received at the same time – and what the laboratory capacity is, taking into account the staff and equipment to analyze the samples.

Lab manning is another factor. As the demand for testing has increased, laboratories are having a hard time adding enough staff. The requirements vary from state to state, Garner says, but those who analyze the tests must be clinical laboratory researchers with education and experience. And like other companies, labs deal with employees who contract COVID-19 and have to leave work to isolate themselves.

Potential laboratory staff should also do well in a high-pressure situation, Kelly says. His company has hired 30 more workers within the last 3 weeks, bringing the total number to 160. Some work 7 days a week.

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

While Garner says he is often asked if fake test labs show up, he says he is not aware of any. And it’s easy enough to check a lab’s credentials.

Legitimate laboratories are certified under CLIA – Clinical Laboratory Improvement Amendments from 1988. Under CLIA, federal standards apply to all U.S. facilities or locations 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 laboratory by name to verify its certification.

States may also provide certification information and other test details. For example, the California COVID-19 Testing Task Force publishes its laboratory list with details of locations, number of tests performed weekly, and average treatment times.

Analysis in the laboratory

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

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

The PCR test (polymerase chain reaction) detects the genetic material of the virus.

“RNA is extracted from the sample and 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 sample. PCR technology allows researchers to amplify small amounts of the RNA from the samples into DNA, which is replicated until viruses are detected.

One of the chemicals produces a 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, medical director of Paradigm Site Services.

Once the analysis begins, it is possible to estimate how long the results will take, Milner says.

The longest analysis is for the PCR test, which varies from lab to lab, but which often takes about 1.5 to 2 hours, he says. The antigen test “takes no more than 20 minutes,” says Milner.

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

Facilities that offer fast tests may only perform COVID tests and may process the tests in the same location, Milner says, enabling faster processing. “If they are CLIA certified, the quality of that test should be OK,” he says.

A laboratory’s definition of processing time for the non-rapid tests may differ from the person awaiting the result. Quest Diagnostics, for example, says its treatment timeline starts at the end of the day whereupon the sample is collected and ends at the end of the day on which results are reported.

Confirmation of results

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

But the test is repeated if the initial result is not conclusive, Garner says. And if it is not crucial for the second time? “We’re releasing it indefinitely,” and another test can be ordered.

When they are finished, the results are sent via text message or email.

Long-term solutions

As no slowdown in demand is expected in the near future, long-term corrections are needed.

“From a laboratory standpoint, we’re all so frustrated that we do not have the infrastructure and capacity to meet the need,” says Garner. “In general, we have not built the test infrastructure needed to combat the pandemic.”

At the outset of the pandemic, he says, when demand first rose, “we should have looked at it as a need to build infrastructure.”

Meanwhile, laboratory directors know how important timely results are, but will not sacrifice speed for accuracy. “We want to make sure it gets done right,” Kelly says.


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