Why your COVID test results take so long


January 14, 2022 – As the Omicron variant spreads in the United States, which is now blamed for more than 98% of COVID-19 infections, the demand for laboratory tests has skyrocketed – especially since home antigen testing is scarce. .

There are also growing complaints from test takers who repeat this troubling question:

What takes so long for results?

Promised deadlines of 24 to 48 hours extend to several days, as people wonder whether to isolate themselves or continue with their usual schedule.

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

“You’ll be surprised at the delays,” said Dan Milner, Ph.D., chief medical officer of the American Society of Clinical Pathology, a laboratory organization.

The journey of the nasal tampon – from the place of collection to the test results arriving by text or email – is more engaging and complex than most people realize, say Milner and other experts. Many steps along the way, as well as staffing and other issues, including outbreaks of COVID-19 among laboratory staff, can slow down the execution of results.

First, the problem with volume

National statistics, as well as daily calculations by individual laboratories, reflect a boom in test requests.

On January 11, the average number of tests for COVID-19 in the United States reached nearly 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 locations in the United States, had registered 67.6 million COVID tests since launching the service in 2020. That’s an increase of about 3 million since December 21, when they were 64.7 million.

UCLA’s Clinical Microbiology Laboratory now handles more than 2,000 COVID tests each day, up from 700 or 800 a month ago, said Dr. Omay B. Garner, director of clinical microbiology for UCLA’s health system. And he doesn’t think demand has peaked.

In Tucson, Arizona, Paradigm Site Services, which contracts with local governments, businesses and others to provide tests, is performing 4,000 tests a day, compared to a daily number of 1,000 in early November, said Stephen Kelly, chief executive director.

Beyond the volume, there are other barriers that hinder the planned implementation time.

Taking tampons, taking, transporting

“People misunderstand the whole process,” Garner said. One big misconception is that the tampon is analyzed exactly at the place of collection. This is usually not true – with some fast (and expensive) PCR test sites sometimes an exception.

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

“Someone can take a tampon and the tampon has to go out of condition,” Garner said.

And even a tampon that is transported by courier to a local testing lab can take longer than expected if traffic is congested or the weather worsens.

Along the way, temperature control is important, says Kelly of Paradigm. “Samples should be stored at the correct temperatures.” Couriers often store specimens in refrigerators to transport them.

Arrival at the laboratory

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

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

Another factor is the staff in the laboratory. As the demand for tests has increased, laboratories are finding it difficult to add enough staff. Requirements vary from country to country, Garner said, but those who analyze the tests must be trained by a clinical laboratory with training and experience. And like other companies, labs deal with employees who become infected with COVID-19 and have to quit to isolate themselves.

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

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

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

Legitimate laboratories are certified under CLIA – Amendments to Improve Clinical Laboratory since 1988. According to CLIA, federal standards apply to all facilities or sites in the United States that test human samples for health assessment or for diagnosing, preventing or treating disease. The CDC has a CLIA Lab Search Tool to search a lab by name to verify its certification.

States may also provide information on certification and other test details. For example, the COVID-19 Test Working Group in California has published its list of laboratories, describing locations, the number of tests performed per week, and the average execution time.

Laboratory analysis

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

“Laboratory antigen tests are not much different” from rapid home tests, Milner said. 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.

“RNA is extracted from the sample and purified using our extraction tool,” said Mariah Corbitt, 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 that replicates until a virus is found.

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 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 take, Milner said.

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

In the case of fast PCR tests, which promise results in 1-2 hours or even less, but can cost $ 300, the processing time can be changed to get results faster, Milner said. And in general, a positive result manifests itself 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.”

Equipment that offers rapid tests can only do COVID tests and can process tests in the same place, Milner said, which allows for faster execution. “If they are CLIA certified, the quality of this test should be fine,” he said.

The laboratory’s definition of the time to perform the rapid tests may differ from that of the person waiting for the result. Quest Diagnostics, for example, says the lead time starts at the end of the day on which the sample is collected and ends at the end of the day on which the results are reported.

Check the results

As such, a positive result is reported, as well as a negative one. “There are no confirmation tests,” Garner said. “That’s why laboratories need to run reliable tests.”

But the test is repeated if the initial result is not convincing, says Garner. And if it is not final for the second time? “We present it as indefinite” and another test can be ordered.

After finalization, the results are sent by text or email.

Long-term solutions

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

“From a laboratory perspective, we are all so disappointed that we don’t have the infrastructure and capacity to meet the needs,” Garner said. “In general, we have not built the necessary test infrastructure to combat the pandemic.

At the start of the pandemic, he said, when demand first increased, “we had to look at it as a need to build infrastructure.”

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



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