Why it takes so long for most COVID-19 test results to be available: Recordings

Mar 28, 2020 10:30 PM ET

After an initial oral exam, a driver receives a COVID-19 nasal swab test from a clothed health worker at a ramp in Daly City, California.

After a slow start, tests for COVID-19 have increased in the past few weeks. Huge commercial laboratories have gotten to work, drive-up test sites have been set up in some places, and new types of tests have been approved according to the emergency rules established by the Food and Drug Administration.

But even for people who are able to test (and there is still a big lag in testing skills at hotspots in the U.S.), it can be frustratingly long to get results – not just hours, but often Days. Even Senator Rand Paul, R-Ky., Received no positive test results for six days and was criticized for not quarantining himself during that time.

We asked experts to explain why the processing time for results can vary widely – from hours to days or even a week – and how this may change.

It is a multi-step process

First, a sample is taken from a patient’s nose or throat using a special swab. This swab goes into a tube and is sent to a laboratory. Some large hospitals have on-site molecular test laboratories, but most samples are sent to external laboratories for processing. More on that later.

This transit time is usually around 24 hours, but can be longer depending on how far the hospital is from the processing laboratory.

The sample is processed in the laboratory, which means that laboratory workers extract the RNA of the virus, the molecule that helps regulate genes.

“This purification step – the RNA extraction step – is a limiting factor,” said Cathie Klapperich, vice chair of the biomedical engineering department at Boston University. “Only the largest laboratories have automated methods to extract RNA from a sample and do it quickly.”

After extracting the RNA, technicians must also carefully mix special chemicals with each sample and run these combinations in a machine for analysis. This process is called the polymerase chain reaction and can determine whether the sample is positive or negative for COVID.

A laboratory technician adds vials to a Covid-19 polymerase chain reaction tester at a Co-Diagnostics Inc. facility in Salt Lake City.

“A PCR test typically takes six hours from start to finish,” says Kelly Wroblewski, director of infectious disease programs at the Association of Public Health Laboratories.

Some laboratories have more staff and more machines, so more tests can be run at the same time than others. But even for these laboratories, the backlog increases with increasing demand.

Capacity is growing, but not fast enough

Initially, only a few public health laboratories and the federal centers for disease control and prevention processed COVID-19 tests. Problems with the first CDC test kits also caused delays.

Now the CDC has a better kit and 94 public health laboratories across the country are doing COVID-19 tests, says Wroblewski.

But these laboratories cannot possibly do everything that is needed. In normal times, her primary function is to monitor public health on a regular basis – to identify more common threats such as measles outbreaks or to monitor seasonal influenza – “but not to run diagnostic tests of the magnitude required for this response,” she says.

Large commercial laboratories, such as those of companies like Quest Diagnostics and LabCorp, received FDA approval at the end of last month to begin testing as well.

The FDA has announced that it will not prevent certain private laboratories and universities – and diagnostic companies – from developing their own test kits. This includes laboratories in some well-known hospital systems such as Advent Health, the Cleveland Clinic and the University of Washington.

In addition, the FDA has approved more than a dozen test kits from various manufacturers or laboratories according to special emergency rules to speed up the process. This includes tests from Quest Diagnostics, LabCorp, Roche, Quidel Corp. and others. The kits are used in PCR equipment, either in hospital laboratories or in large commercial laboratories.

“A chief medical officer on the east coast said it took an average of 72 hours to get results until two days ago,” said Susan Van Meter, managing director of AdvaMedDx, a division of the Advanced Medical Technology Association, a device group that specializes in the device and diagnostics industry . “It will be better if our member companies come onto the market.”

Still, supply can’t keep up with demand, Roche’s CEO Severin Schwan told CNBC on Monday. Roche received first FDA approval for an emergency test kit and has delivered more than 400,000 kits to date.

“Demand continues to be much higher than supply,” Schwan told CNBC. “So we are happy that the total capacity is increasing, but the reality is that wide-ranging tests are not yet possible.”

How many tests can be run at the same time?

That is different. Large commercial laboratories can do a lot. For example, LabCorp says it processes 20,000 tests a day – and hopes to do more soon. Other test kit manufacturers and laboratories are also increasing their capacity.

Smaller laboratories – such as B. Molecular testing labs in some hospitals – can do far less per day, but get results faster for patients because they save transit time.

Still, only large academic medical centers and some health systems usually have their own molecular testing labs that require complex equipment.

One of them is the Medstar Georgetown University Hospital in Washington, D.C.

“From the start, the result can take five to six hours,” said Joeffrey Chahine, technical director of the molecular pathology department there.

Even in such hospitals, tests are often prioritized for patients who have been admitted and for employees who may have been exposed to COVID-19, Chahine says. His laboratory can process 93 samples simultaneously and run a few cycles a day – up to 279 tests a day, he says.

A doctor examined Juan Vasquez last week as part of a COVID-19 exam in a test tent outside the St. Barnabas Hospital emergency room in New York City.

But even hospitals with this ability generally don’t “test in their outpatient clinics or emergency rooms,” he says – in other words, no tests are performed on walk-in patients in the in-house laboratories. These tests are sent to large external laboratories “so as not to overwhelm the hospital laboratory”.

While these external laboratories have large employees, “the demand is so high that these outpatient clinics and emergency rooms say that the processing time can be four to seven working days,” says Chahine.

Delivery bottlenecks slow test production

As global demand for tests increases, so too does the lack of chemical agents used in the test kits, the swabs used to take the samples, and the protective masks and equipment used by health workers who take the samples .

“There is an inadequate supply of so many things related to testing,” says Wroblewski, which is why her group, along with officials in states like New York and cities like Los Angeles, recommends prioritizing who will be tested on COVID-19 should.

At the top of the line, she says, should be healthcare workers and first aiders; older adults with symptoms, especially those who live in nursing homes or assisted dormitories; and people who may have other diseases that would be treated differently if they were infected.

Conclusion: The prioritization of the people tested helps to reduce the processing time in order to achieve results for people under these circumstances and to reduce the risk of the disease spreading.

However, the urgent lack of some of the chemicals required to perform the tests is hampering efforts to test healthcare workers, including in hospitals such as SUNY Downstate Medical Center in hard-hit New York.

With a view to the future, companies are working on faster tests. The FDA has recently approved tests from two companies that promise results in 45 minutes or less. However, these will only be available in hospitals that have special equipment to perform them. One of these companies, Cepheid of Sunnyvale, California, says that approximately 5,000 U.S. hospitals already have the equipment necessary to perform these tests. Both companies say that they will deliver to the hospitals soon, but have provided little information about the quantity or timing.

However, many public health officials say that general practitioners and clinics need a really quick test to do in their offices – one like the tests that are already done for influenza or strep throat.

A number of companies are moving in this direction. For example, late Friday, Abbott Laboratories announced that the FDA has granted emergency approval for the company’s rapid point-of-care test, which can produce positive results in just five minutes and negative results in 13 minutes.

The tests are processed on a small device that is already installed in thousands of medical practices, emergency rooms, emergency clinics and other facilities. Abbott said it would start delivering 50,000 tests a day next week.

“This will make a significant difference,” said AdvaMedDx’s Van Meter, who believes that rapid testing is an important additional part of the continuum of available tests.

Although laboratory-based PCR tests performed in large laboratories and academic medical centers can take several hours to achieve a result, the equipment used can test a large number of cases at the same time. Abbott’s rapid test – and other similar tests being developed – run at a much slower time, but deliver much faster results.

“This can be done in a doctor’s office or an emergency room to examine patients who are waiting to get in,” says Van Meter. “It is a very good addition to the existing tests.”

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