Despite faint positive Abbott RAT, my (well-collected) PCR was negative.
BACK to MED SCHOOL people. Now listen up back there.....
SARS-CoV-2 virus = beta coronavirus
An enveloped single stranded RNA virus
16 nonstructural proteins
4 structural proteins:
- Spike (S)
- Envelope (E)
- membrane (M)
- nucleocapsid (N)
SARS-CoV-2 = Severe Acute Respiratory Syndrome Coronavirus 2 virus (as compared with the SARS-CoV-1)
Causes no symptoms to mild symptoms such as a common cold (common to a lot of Beta coronaviruses)
Also causes Covid 19 = Coronavirus Disease 2019
The virus access host cells through the Angiotensin converter Enzyme receptor (think of it like a locked gate). The key to the receptor/gate is the Spike protein
RT-PCR: Real time reverse transcriptase polymerase chain reaction.
A technique to amplify certain RNA in the sample
A Diagnostic tool for presence of SARS-CoV-2 RNA
Omicron causes a drop out of the S section of the RNA due to the number of mutations in the RNA
RAT: qualitative rapid antigen test
Not a diagnostic tool, rather a screening test
The difference between Screening and Diagnostic tests:
What happens on a RAT test:
There is a membrane strip
Precoated with mouse derived anti-SARS-CoV-2 nucleocapsid protein (N) antibody at the T line and mouse derived monoclonal anti-chicken IgY at the C line.
some RAT tests use gold colloidal nanoparticles immunochromatography is used to qualitatively determine the presence of SARS-CoV-2 antigens. The gold naopoarticles give the T and C lines its colour because they are concentrated at the T or C line according to whether it binds to the T line or C line antibodies.
Half of the Gold colloidal nanoparticles are coated with monoclonal SARS-CoV-2 antibodies with human IgG specificity
Half of the gold colloidal nanoparticles are coated with monoclonal chicken IgY
- these are called conjugates - they help the binding process.
Drop the specimen into the well
If no human Covid specific IgG, then the fluid will move up the test strip and the only gold nanoparticles that will concentrate at one of the 2 strips will the the chicken IgY ones - causing the C line to light up.
If human IgG is in the specimen then it will bind to the gold nanoparticles with the SARs antibody which will then bind to the SARS antibodies on the T line causing the T line to light up. its setup in such a way that if there are no antibodies in the specimen the gold nanoparticle with SARS-Cov2 will not bind to the antibody on the T line. Whereas the chicken gold antibody will.
As humans don't have anti chicken antibody the C line becomes a control line
If C line does not light up then something is wrong with the test strip and the test is invalid.
Some RATs use UV immunochemistry - these have conjugates which light up with UV light.
In short the RATS and PCR test are used for different purposes, even though the govt thinks they are like for like replacements.
Even though the RAT tests are testing for "antigens" they are really testing for the presence of antibody in the nose or saliva.
Ihe word antigen is that which binds to an antibody - in this case the antibody is on the test strip and the antibody from the nose Plus the conjugate gold become the antigen.
OK lunch break people.
