（Source: Reuters）

Omicron subvariants BA.4 and BA.5 now are responsible for the surge of cases globally. New studies suggest that BA.4 and BA.5 are so far the most transmissible variants. World Health Organization experts has recognized BA.4 and BA.5 continue to drive waves of cases, hospitalisation and death around the world. In April this year, Goldsite released study of Inclusivity on SARS-CoV-2 Antigen Kit (Colloidal Gold) for both professional use and self-testing, to assess its detection ability of emerging Variants of Concern, where BA.4 and BA.5 are included. The study suggests that the kit is working equally effective when detecting the currently prevalent SARS-CoV-2 variants. Goldsite will continue to monitor the impact of the circulating and emerging variants on the performance of the kit. Below is the summary of the study.

Study of Inclusivity (Analytical Reactivity)

April 2022

Product: SARS-CoV-2 Antigen Kit (Colloidal Gold)

Manufacturer: Goldsite Diagnostics Inc.

Aim of the study

The aim of the study to evaluate the kit’s performance in detecting the emerging SARS-CoV-2 variants.

Procedure

11 variants of concern that are circulating, had been circulating or identified as clinically significant were evaluated in this study. The samples for testing were either inactivated virus or recombinant viral nucleocapsid proteins (NP) if the virus culture was not available. The inactivated virus was kindly provided by Guangzhou Customs Technology Center. The identities of these virus stocks were determined by 2^nd generation sequencing. Information of the variants for testing was summarized in the table below. All the samples were diluted with negative sample matrix (pooled negative nasal swabs eluted in saline) to two concentrations: one is low positive (3.33 x 10² TCID₅₀/mL for inactivated virus or 2.5 ng/mL for NP), the other is middle positive (1 x 10³ TCID₅₀/mL for inactivated virus or 7.5 ng/mL for NP). The low positive and middle positive concentrations correspond to 1 x Limit of Detection (LoD) and 3x LoD, respectively, of the kit determined using the wild-type virus. Swabs (the same swab that is provided with the kit) were soaked in the dilution and tested according to the test procedure. Each dilution was tested in 20 replicates.

Table 1 Variants tested in the inclusivity study

1) The NP of BA.4 shared identical mutations with NP of BA.2 except for that BA.4 has an additional mutation at P151S.

2) The NP of BA.5 shares identical mutations with that of BA.2.

3) XD is an Omicron/Delta recombinant. The NP of this recombinant is from the Delta variant.

4) XE is a BA.1/BA.2 recombinant. The NP of this recombinant is from the BA.2 variant.

5) XF is an Omicron/Delta recombinant. The NP of this recombinant is from the Omicron BA.1 variant.

Results

Each of the sample dilution was tested in 20 replicates. The results were as follows:

Table 2 Detection of the variants using SARS-CoV-2 Antigen Kit (Colloidal Gold)

Conclusion

The results showed all variants of concern can be detected ≥ 95% of the time when diluted to the original LoD determined with the wild type SARS-CoV-2 virus. When diluted to 3 x LoD concentrations, all variant dilutions can be detected 100% of the time, and the testing line color was uniform across all the replicates tested indicating good precision. In conclusion, the kit is working equally effective when detecting the currently prevalent SARS-CoV-2 variants. The company will continue to monitor the impact of the circulating and emerging variants on the performance of the kit

Center of Reagent Research and Development

Goldsite Diagnostics Inc.