IIRC, the class of antibody we develop in the upper airways and mouth mucosa - IgA - reacts much faster and in greater quantity than IgM and IgG. Can be used to detect this kind of stuff much faster and earlier in the cycle than the other ones.
Also is one of the reasons why there's a lot of studies into making breathable vaccines for respiratory diseases.
That might be true - I actually have no clue and never read anything on that topic - but the studies I read were about PCR testing with saliva instead of mucosa as the substrate. So direct testing of virus presence in the sample.
Antibody tests are still not recommended and not approved to detect or rule out an active infection in my country - except for very specific circumstances like strong clinical symptoms but multiple negative tests for viral material (PCR, etc).
Australia has saliva testing available as a backup, has for a while now. It's offered to people who would otherwise refuse the nasal swab or elderly/young children where its easier on them. Our health experts say it's not as good as a nasal swab (Which is why it's a backup) but, it's good enough for use
The thing is: nobody actually knows, because we don't have good, publicised and peer-reviewed large scale studies for ANY SARS-CoV-2 test yet!
Gold standard is a proper nasopharyngeal swap - if they were "not that far up" it was anterior nasal or a conchal swab and they're not.as.good even though the US CDC recalled it's preference for nasopharyngeal swabs (probably a political call or to conform to the realities on the ground, the US has so many tests and such long lines on the drive-ins that you see in the media that a proper NP swab by medical staff in proper PPE is probably impossible) - but even there studies/papers so far never achieved 100% sensitivity even on patients hospitalised for Covid-19! The best timeframe after a possible infection to have maximal viral load in the mucosa of the upper respiratory tract, best swab design, etc. are still not empirically proven and just educated guesses, so to say.
So the nasal swab can't be properly evaluated yet with the four square method (or whatever you call that false positive/correctly positive/false negative/correctly negative chart in English) for the SOP that we will use in the future. So no other test can be properly compared to it, either!
One of the studies had a somewhat overlapping confidence interval (with saliva test on the lower end of the spectrum) and some paired studies had a small, but - if I remember correctly, I just got out of bed - already significant number of positive tests were the nasal swab was negative. In one it was...two...though, because the amount of data points we have right now sucks.
My department of public health that I volunteered for sticks to nasopharyngeal swabs on the basis of the studies I looked up and shared, but saliva based PCR tests look promising and would make mass testing in schools a lot less nerve wracking. If we ever have to do that instead of a class or two as it was before the summer holidays started🤷♀️
The turnaround time is still took long. If we had something instant, that would be a game changer. This will help, but it's not the megabomb that twitter thread is making it sound out to be.
The actual PCR test in the lab is not that long. Depending on the # of cycles it's a couple of hours, for Corona I was told it's about 5 hours or so, max.
We have different labs that we have tests done in, the Viro lab of our university hospital and a privatly run one. The Viro lab has to copy their results and manually transfer them into our database, the other has an automated data transfer AFAIK and a much larger testing capacity for SARS-CoV-2 because they simply bought a PCR "robot" that handles large amounts of vials in no time. So one takes 24-48 hours usually, the other sometimes has some of the results up in the evening.
Rapid/point-of-care tests exist and students in our test drive-in are part of a study to validate it...but we have to few positive cases ourselves to compare their results to, so they can't evaluate test sensitivity 🤣 They are trying to get samples out of the USA to test against, they have enough positive ones 🤷♀️
