Why don’t they use scanning electron microscopy to detect coronavirus vs. a very inaccurate PCR test?
pcr can be run in 96 or 384 well plates in a reaction taking 60-90 minutes on equipment costing a few thousand pounds which are easy to use . I do not know how many samples a day SEM can process but I am sure that a small error rate is compensated by tha ability to cheaply run thousands more samples per machine per day
pcr can be run in 96 or 384 well plates in a reaction taking 60-90 minutes on equipment costing a few thousand pounds which are easy to use . I do not know how many samples a day SEM can process but I am sure that a small error rate is compensated by tha ability to cheaply run thousands more samples per machine per day
In addition to Paul’s answer, I don’t see how SEM could allow to distinguish between SARS Cov2 and any other coronavirus look alike.
Beyond Mr. Rutland's cogent point, PCR has recently gotten a bad rap mostly due to production/distribution errors. Its more than accurate enough to give clinically relevant information when the reagents used are not contaminated or denatured. Like any other mass produced thing, the more you produce the greater the probability of defective products. If SEM was the main testing method, we'd be talking about how SEMs are constantly breaking down, use buggy software, are overpriced, low-throughput etc. People would be asking why we're not using PCR instead.
Just from talking to people ( aside from scientific literature) I found out that PCR can pick up remnants of other coronaviruses, even non-culturable. Thus giving false positive results as well as false negative. Then with a false positive result the person runs in a hospital, where he really gets a big virus load.
Natalia S Duxbury I would point out that PCR can be highly stringent and very specific or can be fairly loose and non-specific. It is all a matter of the primer design. So to say that PCR gives false positives is not really accurate. A given PCR test kit might give false positives and another one might not. As with most tests there is a compromise, do you tilt the balance to catching every positive case but end up with some false positives, or do you balance it so you never have false positives but you have false negatives.
No method or test is 100% accurate and correct and iIt isn't the technique but rather how the test was designed and used. This is true for PCR, for antibody tests, and also for any sort of analytical test.
In a practical sense it is better to have a test that picks up nearly all cases but has some false positives because this allows one to isolate and treat the group that can transmit the disease. False negatives are more of a problem as that allows infected people to move around socially and spread the disease. It depends really on whether you are trying to protect the population or the individual as a priority.
The variation mutants of COVID-19 can cause false-negative results in RT-PCR if the PCR test system does not include all variations detection primer set. In the case of scanning electron microscopy, the detection efficiency is high but the time for analysis is very long in comparison with PCR or ELIZA test.
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