bulldog10 wrote:
I have talked with several people at SL getting the test with me and there was some confusion. There is a bit of science below, ignore the post if it’s too technical. Basically there are three tests:
PCR: is detecting genetic material from the virus. It is the most sensitive and also least likely to give a false positive. It is the most complicated laboratory procedure which takes time and costs more. Usually overnight.
Antigen: Is also a direct test for virus that is present. The antigen test is detecting a virus protein instead of genetic material. The protein is on the outside of the virus. This is old school technology. Essentially the same technology as a pregnancy test. Only difference is they have changed which protein is detected and how the sample is collected.
Can be done rapidly. Not quite as fast as pissing on a stick, but close. They need to use a sterile solution to get the virus off the swab, then run that solution over the test strip. This is what they are doing in the two hour tests.
Both of the above tests are looking for virus that is currently present. Both use nasal swab. Both are accepted to return to US.
Antibody: Detecting if your immune system has been exposed. Need a blood sample. Will be positive for months after exposure or vaccination. Long after no virus is present. Should be used only in special circumstances. Not accepted to return to US.
Forget about the Antibody test. It is NOT valid for travel and over time becomes less of a measurement of any value.
The downside to the Antigen test a/k/a rapid test is the risk of a false positive result (just like a pregnancy test). So, if you test positive with the Antigen test, but otherwise feel fine, then you will certainly need to follow up with a PCR test while waiting and dealing with the implication that you "maybe" have Covid-19 and aren't allowed to travel on an airplane.
If you are paying for a test, then perhaps it is better to pay a little more and wait a few hours longer for a test that is actually accurate, especially if you do not already feel sick or have already been vaccinated.
But, some people may still prefer the rapid test, in particular if they already have symptoms of Covid-19 and want quick confirmation of the illness.
https://www.memorialhealthcare.org/what ... prc-tests/https://www.hearthsidemedicine.com/post ... w-accurate