1 gene COVID-19 assay testing9 Jun 2020 15:59
The worry with 1 design target is that it isn't specific enough to exclusively detect SARS-CoV-2, the virus causing COVID-19 due to lack of available sequence information. However the WHO guidance for this has changed so 3 designs were originally chosen as the protocol to improve confidence in the test but this was reduced to two on January 17th, this was reduced to 2 targets due to the 3rd having lack of sensitivity.
@Yourgene tweet: Jargon busting #1 Detection Rate (Sensitivity) - This is the number of cases that are correctly identified using the test. For example a detection rate of 99% means that out of every 100 cases, 99 would be identified. This detection rate has a low false negative rate.
On 17th March 2020, the WHO issued interim guidance to say in areas where COVID-19 virus is widely spread a simpler algorithm by rRT-PCR of a single discriminatory target is considered sufficient.
Hence Primerdesign/Bioinformatics Scientist designing the 1 gene COVID-19 assay and gaining WHO approval.
What does this means? Once a virus is well established in a population, variation within a virus is less likely to occur. Hence 1 gene is okay. The two-assay approach provides some redundancy so that if one assay starts to accumulate mutations, which is a particular risk with an RNA genome, the other one should still give a positive result in the presence of the target.
@Yourgene tweet: Jargon busting #3 False Positive Rate – This is the number of cases where that are incorrectly identified as having the condition when in fact, the person is unaffected.
Novacyt/Primerdesign's strategy was to design one assay which was specific to the SARS-CoV-2 coronavirus which was both sensitive and robust, to enable detection of the virus without the need to use a dual assay approach as this was the strategy used in their previous RUO qPCR kits.
The frustration then for Novacyt holders is that their test is consistent with WHO guidelines but not accepted by French authorities as now being the gold standard. Whether the same investor attention they benefited from will benefit YourGene's test when launched will be seen.
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