China has granted approval to five COVID-19 antigen kits made by local companies to be used for self-testing, China Media Group said on Saturday, as a sudden rise of cases are emerging in several cities.

China's National Medical Products Administration (NMPA) published a notice on Friday saying Beijing Huaketai Biotechnology had been allowed to make changes to its COVID-19 antigen test kit's device certificate.

It published a similar approval for four other companies, Nanjing Vazyme Biotech, Guangzhou Wondfo Biotech, Beijing Jinwofu Bioengineering Technology and a BGI Genomics subsidiary, Shenzhen Huada Yinyuan Pharmaceutical Technology, on Saturday.

China's health regulator, the National Health Committee, said on Friday that members of the general public can purchase antigen self-test kits in stores and online.

There was no similar test kits available for public purchase before. 

Nucleic acid test vs. antigen test

"Antigen is like the 'clothes' of the virus, while nucleic acid is the gene of the virus," Zhang Wenhong, a Shanghai-based top infectious disease expert said in an interview.

The nucleic acid test can detect even just a small amount of the virus but requires a lab to process for a longer time compared to an antigen test. An antigen test is rapid since it directly detects the "clothes" of the virus and can be easily used at home by individuals.

"In the early stage of infection, the amount of virus can be very low," Zhang said. "The nucleic acid test can detect it but an antigen test cannot."

Zhang pointed out the use of an antigen test can still be very valuable as potential patients can be easily detected on their own in a rapid manner.

Mass nucleic acid testing has become increasingly challenging due to China's recent COVID-19 flare-ups in many cities. China's daily rise of domestically transmitted cases reached a two-year high this week with many asymptomatic carriers.

Zhang said multiple rapid-test methods will help China to detect COVID-19 cases in time if China plans to loosen travel restrictions.

(With input from Reuters）