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Author: Site Editor Publish Time: 2021-11-29 Origin: Site
November 29th, 2021
With the pandemic outbreak of COVID-19, multiple SARS-CoV-2 virus variants have emerged, including B.1.1.7 lineage (Alpha), B.1.351 lineage (Beta), P.1 lineage (Gamma), B.1.617.2 lineage (Delta), B.1.1.529 (Omicron), etc.
Most of the mutations in these variants occur in the viral surface proteins (e.g. Spike proteins), while few mutations occur in the nucleocapsid (N) because the N protein is essential for virus survival and is too conserved to change.
SARS-CoV-2 Antigen Kit (Colloidal Gold) manufactured by Goldsite Diagnostics Inc. is intended to detect the N protein in human nasal swab specimens. Both the two antibodies used on the test kit target the viral nucleocapsid (N) protein.
Since it is strictly prohibited in China to perform experiments using the live SARS-CoV-2 virus, we used the recombinant nucelocapsid protein of the variants to the test whether the kit performance would be affected by the new variants.
The recombinant nucleocapsid protein (NP) (wild type, delta version, omicron version) of the SARS-CoV-2 was serially diluted with the extraction buffer, to make a series of dilutions with final test concentration shown below. 70 μL of the dilutions was added directly for testing. All dilutions were tested in triplicates. The results were as follows:
Wild type NP | Delta variant NP | Omicron variant NP | |||
Concentration | Result | Concentration | Result | Concentration | Result |
100 ng/mL | 3/3 Positive (+) | 100 ng/mL | 3/3 Positive (+) | 100 ng/mL | 3/3 Positive (+) |
25 ng/mL | 3/3 Positive (+) | 25 ng/mL | 3/3 Positive (+) | 25 ng/mL | 3/3 Positive (+) |
10 ng/mL | 3/3 Positive (+) | 10 ng/mL | 3/3 Positive (+) | 10 ng/mL | 3/3 Positive (+) |
2.5 ng/mL* | 3/3 Positive (+) | 2.5 ng/mL | 3/3 Positive (+) | 2.5 ng/mL | 3/3 Positive (+) |
*The limit of detection (LoD) of the test has previously been determined to be 2.5 ng/mL using the wild type NP.
The preliminary results showed that the test has the same sensitivity (limit of detection, LoD) when detecting the wild-type, the delta variant, and the omicron variant's nucelocapsid proteins, which were 2.5 ng/mL.
Based on preliminary testing results above and the comparison analysis, we hereby declared that SARS-CoV-2 Antigen Kit (Colloidal Gold) performs the same (i.e. no impact) when detecting the SARS-CoV-2 variants including but not limited to the following variants (next page).
Variant | Lineage | First documented in |
Alpha | B.1.1.7 | UK |
Beta | B.1.351 | South Africa |
Gamma | P.1 | Brazil |
Delta | B.1.617.2 | India |
Omicron | B.1.1.529 | mainly South Africa |
Lambda | C.37 | Peru |
Mu | B.1.621 | Columbia |
Vairants including but not limited to the above ones can be detected by SARS-CoV-2 Antigen (Colloidal Gold).
Goldsite Diagnostics Inc. will continue to monitor the impact of the circulating variants on the performance of the kit.
