3 ms·
If you look at the actual testing data for antigen tests [0], the LoD for them is very high compared with PCR. This means a person needs a high viral load for t
by fotta 5y ago
If you look at the actual testing data for antigen tests [0], the LoD for them is very high compared with PCR. This means a person needs a high viral load for tests to be effective. For example, the BinaxNOW kits require 140.6 TCID50/mL [1] vs 0.012 TCID50/mL for a PCR test (I picked a random one here) [2]. The FlowFlex tests are even worse, requiring 2500 TCID50/mL [3]. I personally purchased a few of the Lucira tests (not affiliated I promise) because they're more similar to an at-home PCR (they use LAMP) and so the LoD is lower (0.9 TCID50/mL) [4].
[0] https://www.fda.gov/medical-devices/coronavirus-disease-2019-covid-19-emergency-use-authorizations-medical-devices/in-vitro-diagnostics-euas-antigen-diagnostic-tests-sars-cov-2 https://www.fda.gov/medical-devices/coronavirus-disease-2019...
[1] (pdf) https://www.fda.gov/media/141570/download https://www.fda.gov/media/141570/download
[2] (pdf) https://www.fda.gov/media/142193/download https://www.fda.gov/media/142193/download
[3] (pdf) https://www.fda.gov/media/152698/download https://www.fda.gov/media/152698/download
[4] (pdf) https://www.fda.gov/media/147494/download https://www.fda.gov/media/147494/download
- disabled 5y agoWhat unit of measurement is TCID50/ML? Just curious
- h2hq 5y agohttps://iamanovice.wordpress.com/2011/03/31/tcid50/ https://iamanovice.wordpress.com/2011/03/31/tcid50/
- fotta 5y agoI am admittedly not a virology expert but my understanding is TCID50 signifies the concentration at which 50% of the cells are infected when the sample is inoculated with a diluted solution of viral fluid. Ripped straight from https://www.bio-rad.com/en-us/life-science-research/overlay/analytical-sensitivity-lod?ID=Analytical_1610048637 https://www.bio-rad.com/en-us/life-science-research/overlay/...
- dtech 5y agoThe amount of virus necessary to affect half (50%) of the cells in a sample.
- riedel 5y agoWow those package leaflets are impressive. We (in Germany) get those Chinese test on an emergency admission and all they have is a single table with specifity and sensitivity (no info on viral load at all). They are however cheap and they still work . The responsible agency is actually testing them recently and at least publish the results: https://www.eurosurveillance.org/content/10.2807/1560-7917.ES.2021.26.44.2100441 https://www.eurosurveillance.org/content/10.2807/1560-7917.E... . Still they allow companies to sell obviously nonworking tests with nonreproducible test results.