Why the COVID test results take you so long

January 14, 2022 – As the Omicron variant, which is now blamed for more than 98% of COVID-19 infections, has spread across the United States, the demand for laboratory testing has skyrocketed – mainly because domestic antigen testing is scarce.

There are also rising complaints from test participants who repeat this anxious question:

What takes so long to get results?

The promised turnaround times of 24 to 48 hours drag on to several days as people wonder if they should isolate themselves or continue their regular schedule.

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

“You’d be surprised at the time delays,” said Dan Milner, MD, chief physician for the American Society for Clinical Pathology, an organization for laboratory professionals.

The route of nasal swabs – from the collection site to the test results that arrive in a text message or e-mail – is more complex and complicated than most people realize, Milner and other experts say. Many steps along the way, as well as personnel and other issues, including the outbreak of COVID-19 among laboratory staff, can delay turnaround times for results.

First, Volume Issue

National and daily laboratory statistics reflect a boom in testing requirements.

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

By January 12, Quest Diagnostics, a clinical laboratory with more than 2,000 patient sites in the United States, had recorded 67.6 million COVID tests since the service was launched in 2020. This was an increase of about 3 million since December 21, when their total number was 64.7 million.

The UCLA Clinical Microbiology Lab now processes more than 2,000 COVID tests daily, compared to 700 or 800 months ago, says Omai B. Garner, PhD, director of clinical microbiology for UCLA’s medical 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 conducting 4,000 tests a day, compared to 1,000 daily in early November, says Steven Kelly, CEO.

In addition to volume, there are other obstacles that hamper the intended turnaround time.

Swab collection, collection, transport

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

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

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

And even a swab that is transported by courier to a local testing lab may take longer than expected if the traffic is heavy or the weather worsens.

Temperature control is important along the way, says Kelly of Paradigm. “Samples must be stored at the correct temperatures.” Couriers often store samples in refrigerated boxes so that they can transport them.

Arrival to the laboratory

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

Furthermore, how quickly it is tested depends on the volume of tests received at the same time – and on the capacity of the laboratory, taking into account the staff and equipment for sample analysis.

Another factor is the staffing of laboratories. As the demand for tests has increased, laboratories have difficulty adding enough staff. Requirements vary from state to state, says Garner, but those who analyze tests must be clinical laboratory scientists with training and experience. And like other businesses, the labs handle employees who become infected with COVID-19 and have to leave work in isolation.

Potential lab staff also have to deal well with a situation under high pressure, 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 is often asked if fake test labs are coming up, he says he doesn’t know about any. And it’s pretty easy to check your lab credentials.

Legitimate laboratories are certified by the CLIA – Clinical Laboratory Improvement Supplements, 1988. According to the CLIA, federal standards apply to all U.S. facilities or sites that test human specimens for health assessment or the diagnosis, prevention, or treatment of disease. The CDC has a CLIA Laboratory Search Tool that allows you to search for a laboratory by name and check its certification.

States can also provide information on certification and other testing details. For example, the California Working Group on COVID-19 testing publishes a list of its laboratories with details of location, number of tests performed per week, and average turnaround time.

Laboratory analysis

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

“Laboratory antigen tests are not very different” from rapid home tests, says Milner. A control and test line is used to detect the virus.

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

“RNA is extracted from the sample and purified using our extraction tool,” said Mariah Corbit, compliance manager at Paradigm Laboratories.

Special chemicals and enzymes are added. A PCR device 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 that replicates until any virus present is detected.

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

A PCR test can also give you an idea of ​​how much virus a 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 last, says Milner.

The longest analysis is for a PCR test, which varies from lab to lab but often requires about 1.5 to 2 hours, he says. Analysis of the antigen test “takes a maximum of 20 minutes,” says Milner.

For fast PCR tests that promise results in 1-2 hours or even less, but can cost $ 300, processing time can be changed to get results faster, says Milner. And in general, a positive result will appear 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.”

Devices offering rapid tests can only perform tests on COVID and can process the tests in the same place, says Milner, which allows for a faster turnaround. “If they are CLIA certified, the quality of this test should be fine,” he says.

The laboratory definition of turnaround time for non-rapid tests may differ from the definition of the person waiting for the result. Quest Diagnostics, for example, says its timeline starts at end of the day on which the sample is taken and ends at end of the day on which the results are reported.

Verification of results

A positive result is reported as such as well as a negative one. “There is no confirmatory testing,” says Garner. “That’s why labs have to do reliable tests.”

But the test is repeated if the original result is not conclusive, says Garner. And if it’s not conclusive a second time? “We’re releasing it as vague,” and another test can be ordered.

Upon completion, the results are sent via SMS or e-mail.

Long-term solutions

As demand is not expected to slow down in the near future, long-term repairs are needed.

“From a laboratory standpoint, we’re all so frustrated that we don’t have the infrastructure and capacity to meet the needs,” says Garner. “In general, we have not built the testing infrastructure needed to fight the pandemic.”

At the beginning of the pandemic, he said, when demand first rose, “we should have considered it a need to build infrastructure.”

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

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