Quote:
Originally Posted by Nox
This is very strange... because here at our workplace, most of our recovered folks who tested positive at the onset of their illness continue to test positive for Covid on the PCR test for a couple of months.... I don’t expect to get a negative result until sometime next year, even though I will return to work a lot sooner.
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I have a limited knowledge of how it works, but the test I took is an RT LAMP test. similar to PCR.
Loop-Mediated Isothermal Amplification (LAMP)
Technology overview
Loop-mediated Isothermal Amplification (LAMP) is a similar process to RT-PCR, but instead
of using a series of temperature changes to produce copies of the viral DNA, LAMP is
conducted at a constant temperature of 60-65°C.
The amount of DNA produced in LAMP is much higher than in RT-PCR and a positive test
result can be seen visually without requiring a machine to read the results.
LAMP is a newer technique compared to RT-PCR, but is technically simple and easy for a
trained scientist to perform, making it a potentially useful technique for detection of COVID19. As it is a newer technology, there is less evidence on its use, but diagnostic companies
are currently performing clinical trials to support it.
How it works
LAMP assays for COVID-19 start with the collection of samples from the nose or throat using
a swab, but can also use samples collected using other methods too such as mucus
produced from hard coughing.
Like RT-PCR, the viral RNA in the sample is converted to DNA which allows it to be copied.
The amplification of the viral DNA using LAMP technology and reagents can be detected
when the reaction mixture is turned cloudy due to the production of a chemical called
‘magnesium pyrophosphate’. As this cloudiness can be seen by the naked eye, it allows for
easy diagnosis of COVID-19 by scientists and clinicians.
The accuracy of the results can be improved by using special fluorescent dyes or colour
changing dyes in the reaction mixture.
As the dyes interact with the viral DNA, the intensity of the light or colour change can be
measured to give the approximate number of viral RNA molecules that were initially in the
sample.
What does the test detect?
Like RT-PCR, LAMP detects whether or not viral RNA is present in samples from a patient.
It does this by capturing and amplifying regions of the virus’ genetic material, usually the
Spike protein, N protein, Envelope or multiple regions at once (see virus diagram in RT-PCR
section above).
Samples can be collected in the same way as they are for RT-PCR, usually from the nose or
throat using long or short swabs, or through mucus produced when a person coughs
strongly. In order to measure the viral RNA, it must be converted to DNA using an enzyme
and copied many times. The results of the test are determined based on the cloudiness or
colour change of the reaction mixture.
What does the result mean?
Like RT-PCR, LAMP tests are highly sensitive and reliable if performed on a sample from
an infected part of the body whilst an active infection is occurring.
Positive test result: - A positive LAMP result means that the person the sample was taken
from is currently infected by the virus.
Negative test result: - A negative LAMP result could mean that the person is not currently
infected by this virus, the virus is not present at the site the sample was taken from, or that it
is too early, or too late in the infection to detect replicating virus. This is why when test
results are negative, new patient samples are taken a few days later to reduce the chance of
incorrectly missing an infected person.