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Why are pcr test results taking so long - why are pcr test results taking so long
After a slow start, testing for COVID has ramped up in recent weeks, with giant commercial labs jumping into the effort, drive-up testing sites established in some places and new types of tests approved under emergency rules set by the Food and Drug Administration.
Rand Paul, R-Ky. Kaiser Health News asked experts to help explain why the turn-around time for results can vary widely — from hours to days or even a week — and how that might be changing. That swab goes into a tube and is sent to a lab.
Some large hospitals have on-site molecular test labs, but most samples are sent to outside labs for processing. More on that later. Oregon hit delays early on because of a shortage of swabs.
That transit time usually runs about 24 hours, but it could be longer, depending on how far the hospital is from the processing lab.
After the RNA is extracted, technicians also must carefully mix special chemicals with each sample and run those combinations in a machine for analysis, a process called polymerase chain reaction, which can detect whether the sample is positive or negative for COVID. Some labs have larger staffs and more machines, so they can process more tests at a time than others. But even for those labs, as demand grows, so does the backlog. Problems with the first CDC test kits also led to delays.
Large commercial labs like those run by companies such as Quest Diagnostics and LabCorp were given the go-ahead late last month by the FDA to start testing too. Labs at some big-name hospital systems, such as Advent Health, the Cleveland Clinic and the University of Washington, are among those doing this.
In addition, the FDA has approved more than a dozen testing kits by various manufacturers or labs under special emergency rules designed to speed the process.
The kits are used in polymerase chain reaction machines, either in hospital labs or large commercial labs. Roche won the first approval from the FDA for a test kit under emergency rules, and it has delivered more than , kits so far.
That varies. Large commercial labs can do a lot. LabCorp, for example, said it is processing 20, tests a day — and hopes to do more soon. Other test kit makers and labs are also ramping up capacity. Smaller labs — such as molecular labs at some hospitals — can do far fewer per day but get results to patients faster because they save on transit time.
Even at such hospitals, the tests are often prioritized for patients who have been admitted and staff who might have been exposed to COVID, said Chahine. His lab can process 93 samples at a time and run a few cycles a day, up to about , he said. Last week, it did a day, three days in a row. As the worldwide demand for testing has grown, so, too, have shortages of the chemical agents used in the test kits, the swabs used to get the samples, and the protective masks and gear used by health workers taking the samples.
At the front of the line, she said, should be health care workers and first responders; older adults who have symptoms, especially those living in nursing homes or assisted living residences; and people who may have other illnesses that would be treated differently if they were infected. Bottom line: prioritizing who is tested will help speed the turnaround time for getting results to people in these circumstances and reduce their risk of spreading the illness. Still, urgent shortages of some of the chemicals needed to process the tests are hampering efforts to test health care workers, including at hospitals such as SUNY Downstate medical center in hard-hit New York.
Looking forward, companies are working on quicker tests. Indeed, the FDA in recent days has approved tests from two companies that promise results in 45 minutes or less. Those will be available only in hospitals that have special equipment to run them. One of those companies, Cepheid of Sunnyvale, California, says about 5, U. Both firms say they will ship to the hospitals soon but have given few specifics on quantity or timing.
But many public health officials say doctors and clinics need a truly rapid test they can use in their offices, one like the tests already in use for influenza or strep throat. A number of companies are moving in that direction. The tests are processed on a small device already installed in thousands of medical offices, ERs, urgent care clinics and other settings.
Abbott said it will begin this week to make 50, tests available per day. Even though lab-based PCR tests, which are done at large labs and academic medical centers, can take several hours to produce a result, the machines used can test high numbers of cases all at once.
The rapid test by Abbott — and other, similar tests now under development — do far fewer at a time but deliver results much faster. It is an editorially independent program of the Henry J. Kaiser Family Foundation which is not affiliated with Kaiser Permanente. Note to readers: if you purchase something through one of our affiliate links we may earn a commission.
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