Interesting info on saliva vs swab covid tests


The Scientist newsletter I get this research was posted this morning.

They compared nose swabs vs saliva testing for covid 19. They did this where everyone got both tests. Research about which was more accurate has been mixed. People tested and then results compared in those other studies were already fairly sick with symptoms and this study was testing entire villages in the Amazon.

They found (amongst other things) that the swab test picked up more asymptomatic cases than the saliva tests. The swab test was more sensitive when someone’s viral load was lower (so more false you don’t have it with saliva under those circumstances) and the swab test was positive longer (they hypothesized that was because - already known from earlier studies - saliva changes over faster and nasal and lung mucus changes over slower so they hold viruses longer).

As an aside about saliva tests. You want to do them first thing in the morning before you have eaten or drunk anything. I do know that with a genetic saliva test done at a university medical center for a disease my first sample didn’t have enough dna in it to test anything. Reading that article apparently the saliva tests are affected by whether or not it is done the first thing in the morning before you have eaten or drunk anything… I had given the spit sample maybe 2 hours after lunch. On the repeat test they told me to do it first thing in the morning and it had enough DNA in it.