Self-collected swabs for safer, easier #COVID19 testing.
New paper showing sampling done at home moderately sensitive & just misses low viral loads so huge benefit overall. Sound familiar @DanLarremore @michaelmina_lab ?
Short thread
jamanetwork.com/journals/jaman…
New paper showing sampling done at home moderately sensitive & just misses low viral loads so huge benefit overall. Sound familiar @DanLarremore @michaelmina_lab ?
Short thread
jamanetwork.com/journals/jaman…
Background
Testing for #COVID19 continues to be a huge challenge. Part of it is capacity to process the tests but another part is difficulty in doing test. Current standard is nasopharyngeal (NP) swab which involves deep swabbing ("tickling the brain") & requires nurse & PPE.
Testing for #COVID19 continues to be a huge challenge. Part of it is capacity to process the tests but another part is difficulty in doing test. Current standard is nasopharyngeal (NP) swab which involves deep swabbing ("tickling the brain") & requires nurse & PPE.
This puts nurses at risk of infection & requires patients to go to medical provider. We badly need cheap tests that can be done at home so we can test frequently (daily?) & catch high viral loads (i.e. when we are infectious: ).
Low viral loads are rarely infectious () & often will be persistent RNA from an old infection when we aren't infectious anymore (). So tests that are slightly less sensitive b/c they miss low viral loads are still hugely useful.
(Topic for longer discussion: it would actually be BETTER to separate patients by viral load amount not just +/-. No need to isolate patient w/ dead viral RNA; but still need to trace their contacts!)
@DanLarremore @michaelmina_lab have elegant paper showing how missing low viral loads makes tiny difference but frequent testing & delays matter a ton!:
medrxiv.org/content/10.110…
medrxiv.org/content/10.110…
This new paper compares self-collected swabs where swab is inserted into more comfortable part of nose (midnasal swab (MNS) - less brain tickling) w/ standard NP swabs collected by clinician. Sample size isn't huge (N=41), but still instructive.
Of 38 swabs pos by nurse/NP, self/MNS calls 7 (18%) neg, 3 inconclus. (10/38=26% total). Self swabs find 3 more pos that NP say neg.
Initially, this might seem worrisome. You wouldn't want to miss 26% of #COVID patients! But it's not that simple.
Initially, this might seem worrisome. You wouldn't want to miss 26% of #COVID patients! But it's not that simple.
1st: self-swabbing was done an avg of 1 day after NP swabbing. This increases chance of missing viral RNA by ~3% (Fig: day 2 vs 3).
medrxiv.org/content/10.110…
2nd & most important: missed infections were low viral load. Quite low.
medrxiv.org/content/10.110…
2nd & most important: missed infections were low viral load. Quite low.
Missed infections were Ct 33.5-35.1 whereas infections caught were 18.7-26.0 (lower Ct = higher viral load). Same was true for infections that self-swab caught that nurse/NP missed: Ct: 32.7-33.2. These loads are unlikely to have infectious virus:
So, self-swabbing would be highly useful in identifying people that are infectious & have high viral loads & would reduce risks to nurses/clinicians & PPE needs, eliminate need to go to doctor. Extremely useful. Need to pair w/ cheap test still stuck due at FDA.
