Jan 14, 2022 – With the Omicron variant spreading across the United States, which is now blamed for more than 98% of COVID-19 infections, the demand for testing in laboratories is soaring – especially since home antigen tests are scarce.
Complaints are also mounting from test takers, who echo this troubling question:
What takes so long to get results?
Promised durations of 24 to 48 hours span several days, with people wondering if they should isolate or continue with their usual schedule.
The increased size is a major cause of course, but it is not the only one.
“You’d be surprised by the time delay,” says Dan Milner, MD, chief medical officer of the American Society of Clinical Pathology, an organization for laboratory professionals.
Milner and other experts say the journey of a nasal swab — from the point of collection to the arrival of test results by text or email — is more complex than most people realize. The many steps along the way, as well as staffing and other issues, including the COVID-19 outbreak among lab staff, can delay the time it takes to get results.
First, the volume number
National statistics as well as daily statistics from individual labs reflect the surge in test requests.
On January 11, COVID-19 tests in the United States averaged nearly 2 million per day, an increase of 43% over 14 days.
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 they launched the service in 2020. That was an increase of nearly 3 million since December 21, when the total was total. 64.7 million.
At the University of California’s Clinical Microbiology Laboratory, more than 2,000 COVID tests are processed daily, compared to 700 or 800 a month ago, says Omai B. Garner, Ph.D., director of clinical microbiology for UCLA Health System. He does not believe that demand has reached its peak.
In Tucson, Arizona, at Paradigm Site Services, which contracts with local governments, businesses, and others to provide tests, 4,000 tests are being administered daily, compared to the daily number of 1,000 tests in early November, says Stephen Kelly, chief executive.
In addition to size, there are other drawbacks that hinder the required lead time.
Swab collecting, picking up, and transporting
“People misunderstand the whole process,” Garner says. One big misconception is that the swab is analyzed directly at the collection point. This is usually not true – with some fast (and pricey) PCR test sites sometimes being the exception.
Once the nose collection is completed, the sample is sealed in a tube, and then sent to the laboratory. It may be carried by courier to a nearby local lab, or it may be shipped away, especially if collected in a rural area.
“Someone can be swept and the swab needs to get out of the case,” Garner says.
Even a swab delivered by mail to a local testing lab may take longer than expected, if traffic is heavy or the weather is bad.
Temperature control is important down the road, says Paradigm’s Kelly. Samples should be stored at appropriate temperatures. Conveyors often store samples in coolers for transportation.
Access to the laboratory
Once the swab reaches the laboratory, the samples must be logged in.
Then, the speed of its testing depends on the volume of tests received at the same time – and what is the capacity of the laboratory, given the personnel and equipment for analyzing the samples.
Laboratory staff is another factor. With the increasing demand for tests, laboratories are having difficulty adding enough staff. Garner says requirements vary from state to state, but those analyzing the tests should be clinical laboratory scientists with training and experience. And like other companies, the labs handle employees who contract COVID-19 and must leave work to isolate them.
Kelly says prospective lab personnel should handle highly stressful situations. His company has hired another 30 workers in the past three weeks, bringing the total to 160. Some work 7 days a week.
Test equipment – or a lack of it – can slow the process down.
While Garner says he is often asked if there are fake test labs that appear, he says he is not aware of any. It is easy to check lab credentials.
Forensic laboratories are accredited under the CLIA – Clinical Laboratory Improvement Amendments of 1988. Under CLIA, federal standards apply to all US facilities or sites that test human samples for health assessment or for the diagnosis, prevention, or treatment of disease. The CDC has a CLIA lab search tool to search for a lab by name to verify their certification.
States may also provide information on certifications and other test details. For example, the California COVID-19 Testing Task Force publishes its list of labs, detailing locations, the number of tests performed per week, and average response times.
Analysis in the lab
Labs perform two types of tests to detect COVID-19. Antigen tests detect the presence of certain proteins in the virus.
“Laboratory antigen tests are not very different” from rapid home tests, Milner says. There is a control line and a test line used to detect the virus.
Polymerase chain reaction (PCR) tests detect the genetic material of the virus.
“RNA is extracted from the sample and purified via our extraction tool,” says Maria Corbett, director of compliance 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 virus is in the sample. This signal was detected by a PCR machine.
A PCR test can also provide an idea of how much virus a person is carrying, says Chris Johnson, medical director of Paradigm Services.
Once the analysis begins, Milner says, it is possible to estimate how long the results will last.
The longest analysis is the 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 20 minutes at most,” Milner says.
Milner says that in the case of rapid PCR tests, which promise results in one to two hours or even less but can cost $300, the processing time may change to get faster results. In general, a positive result appears faster than a negative result. “If you read it in real time, you can get a positive result in 20 to 30 minutes and report it.”
Milner says facilities that provide rapid tests may only do COVID testing and may process tests at the same location, allowing for faster conversion. “If they’re CLIA certified, the quality of that test should be just fine,” he says.
A laboratory’s definition of response time for non-rapid tests may differ from that of a person waiting for a result. The Task Diagnostic Tool, for example, indicates that the shift schedule begins at end of the day on which the sample is collected and ends at end of the day on which results are reported.
A positive result is reported as such, as is negative. “There is no confirmation test,” Garner says. “That’s why labs need to run reliable tests.”
Garner says the test is repeated if the original result is not conclusive. And if you are not critical the second time? “We called it unspecified” and another test could be ordered.
Once completed, results are sent via text or email.
LONG TERM SOLUTIONS
With a slowdown in demand not expected in the near future, long-term reforms are needed.
“From a lab standpoint, we’re all very frustrated that we don’t have the infrastructure and capacity to meet the need,” Garner says. “Overall, we haven’t built the testing infrastructure needed 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 infrastructure.”
Meanwhile, laboratory managers know how important timely results are, but they will not sacrifice speed for accuracy. “We want to make sure it’s done right,” Kelly says.