Thread by @NathanGrubaugh

Now that our SalivaDirect FDA EUA application for #SARS_CoV_2 diagnostics has been submitted, here is a sneak-peak at our validation results. medRxiv pre-print is forthcoming, but twitter is faster 😉

Overview: saliva w/o special tubes > no RNA extraction > dualplex PCR

1/n

https://twitter.com/NathanGrubaugh/status/1283043299679494153

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About SalivaDirect ➡️ covidtrackerct.com/about-salivadi…

Papers & Protocols ➡️ covidtrackerct.com/saliva-related…

SalivaDirect Results ➡️ covidtrackerct.com/salivadirect-r…

NBA validation study "Swish" ➡️ covidtrackerct.com/swish/

3/n
We validated SalivaDirect with multiple reagents & platforms to:
-make it available to more labs
-avoid specific supply chain bottlenecks
-keep costs down.

We'll provide specific information on how to conduct bridging studies to validate additional reagents/equipement

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We conducted a lower limit of detection study with all of the reagent/equipment combinations using Non-COVID-19 saliva spiked with dilutions COVID-19 saliva.

The LOD = 6-12 virus copies/uL of saliva, depending on the combination.

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Do we need expensive collection tubes to preserve #SARS_CoV_2 RNA in saliva? NO!!

@awyllie13 is about to drop some really nice data on this soon, but here are our prelim results. After 7 days at room temp (RT) or in a 30C incubator, #SARS_CoV_2 RNA detection increases!! 💪

6/n
We also tested SalivaDirect on 52 saliva specimens collected from adults during the 2018/2019 and 2019/2020 (pre-COVID19) autumn/winter influenza seasons, and see *no cross-reactivity*. This is expected based on @VogelsChantal's Nat Med paper:

➡️ nature.com/articles/s4156…

7/n
The real test was clinical validation vs. NP swabs using the EUA approved TaqPath Assay (includes RNA extraction) using patient matched samples.

We found a 94% positive agreement between saliva tested via SalivaDirect and NP swabs via TaqPath.

8/n
Looking at the CT values from our clinical sample type and platform comparisons, we find that patient-matched NP swabs and saliva tested on the TaqPath platform produce similar CT values. So saliva is good (but we knew that 😉)

9/n
We found decreased detection (increased CT values) when testing saliva + SalivaDirect compared to NP swabs + TaqPath or saliva + TaqPath. This is becuase removing RNA extraction does decrease analytical sensitivity, but only by 1-3 CTs.

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What's coming next? Data on pooling, detection of asymptomatic/presymtomatic cases, and practical considerations for scalability. We've come a long way, but still lots to do.