- Why pcr takes time
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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 PCR 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 test can be completed in four to eight hours, however, the results are available in one day due to time taken in collection and in the transportation of samples to the labs. This also adds to the time taken by labs to conduct this test. If the testing lab is far from the place where the sample of the person has been collected, the test result may be available after 48 hours or more, in some cases.
On the other hand, the results of the rapid antigen test can come out in about half an hour but the accuracy is less than that of an RT PCR test. The cost of RT PCR test in private labs has recently been reduced by the Delhi government and is now capped at Rs , if the sample is collected at the facility.
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