Thread by @drmt

What to make of #COVID Ag tests still + at d 8,10,12, etc? There seem to be a lot of them - no data, just anecdotes. But also no data: predictive value of Ag+ for infectious omicron at these time pts. What advice do we give these folks? Don’t test? Isolate? Go to work?

2/ Good evidence that Ag+ = infectious virus for diagnosis. And @CDCDirector @RWalensky initially said the tests weren’t approved for ending isolation. She’s right, & there aren’t robust data on this (to my knowledge - but educate me, please!) We need these data! #IDTwitter

3/ Pre-omicron viral dynamics (from the NBA) showed rapid viral decline, w vaxxed ppl clearing virus faster than unvaxxed (mean 5.5d v 7.5d). This suggests not likely infectious 10+ day time points.
nejm.org/doi/full/10.10…

4/ So if the person is vaxxed (even boosted!), not severely ill, & not immune suppressed, are these persistent Ag+ picking up infectious virus or not? We know this happens w PCR because of exquisite sensitivity, but Ag tests just not that sensitive.

5/ But since we know omicron is more likely to infect upper respiratory tract than delta, could we be seeing higher concentration of virus in nose/throat that persists longer than delta? I’m sure someone out there has done this experiment. Right?

6/ So, I’m eager to hear what guidance #IDTwitter gives to ppl who test to “get out of jail.” There is no rec to test at all in US (Brits test d6&7) and no rec to test again if you do decide to test at d5. But ppl are doing it anyway (if they have tests) to protect others.

7/ Ppl testing repeatedly after +Ag are wasting tests if we think these + are not infectious. But that’s not what we’re taught about Ag tests. And if they are infectious, then we need better guidance on testing to end isolation. Who is doing this work? Thanks, #IDTwitter

Thx @Rebecca4Georgia: descriptive report of omicron kinetics (n=21; 19 vaxxed) from Japan NIID shows peak 3-6d, decreasing viral isolation at d7-9 & no viral isolation at d10 or later, in spite of + PCR, shorter if asx. (Wish they had done Ag tests too!)

niid.go.jp/niid/en/2019-n…