As the omicron variant continues to spread around the world, the demand for rapid antigen tests (RAT) for COVID-19 has also increased. Last month, the White House announced that Americans will be able to start ordering free RATs on January 19, as Washington purchased 1 billion RATs in January.

While Western countries have been relying on RATs as an alternative to their often overloaded PCR-testing system, China remains one of the few countries that almost exclusively relies on PCR tests to identify cases.

PCR tests search for viral genetic material like nucleic acids or RNA while RATs seek pieces of proteins infected by the virus. PCR tests are normally more precise than RATs because they are more sensitive. This means that antigen tests need a higher concentration of the virus than PCR tests to show positive results.

According to data from China's National Medical Products Administration at the end of 2021, China approved 68 new COVID-19 test reagents, including 34 nucleic acid testing reagents, 31 antibody testing reagents, and only three antigen testing reagents.

Chinese-made RATs globally widespread

Even though many RATs manufactured in China haven't been approved domestically, Chinese media reports show that at least 10 kinds of RATs manufactured in China have been approved in countries like the US, UK, Germany, Canada, and Greece.

Some experts think that the reason why China hasn't begun to roll out RATs on a mass scale is because of the country's persistence in enforcing the zero-COVID strategy. "China's upholding of the zero-COVID policy in the foreseeable future determines that rapid antigen tests may not be quite as effective in the current stage," said Xi Chen, an associate professor of health policy and economics at the Yale School of Public Health.

Other experts agree with Chen's assessment. According to Mei-Shang Ho, a research fellow at the Institute of Biomedical Sciences at Academia Sinica in Taiwan, because RATs are not so sensitive to a low viral load, PCR testing is the preferred method for countries upholding the strategy of identifying all existing cases in the community.

"For China, they need to identify all infected people, including the asymptomatic individuals, so it's more accurate for them to reach that goal by relying on PCR tests," she told DW.

The emergence of the omicron varianthas also posed new challenges to the accuracy of RATs. According to Chunhuei Chi, director of the Center for Global Health at Oregon State University in the United States, some recent studies suggest that because the omicron variant may be concentrated more around patients' throats or mouths in the beginning, when they try to take samples from their noses using RATs, the sensitivity of the tests may be lower.

"The real reason for this has yet to be determined, but we now know that the antigen test is less accurate in the face of omicron variants," he told DW.

Will China ever start using RATs?

Experts seem to agree on the fact that as long as China upholds its zero-COVID strategy, it will be unlikely that Beijing begins using RATs on a widespread scale. "Since antigen tests are not so sensitive to low virus loads, the false-negative cases may threaten the zero-Covid strategy," Chen from Yale's School of Public Health told DW.

Chi from Oregon State University also points out that, unlike China, countries that have been using large amounts of RATs have shifted the goal of their pandemic-control measures to preventing serious symptoms and deaths.

"If the goal is to prevent serious symptoms and death, as well as to prevent hospitals from being overloaded, then these countries don't need to care too much about how accurate the tests are," he explained. "What they care about is preventing the number of infections from getting out of control.”

Additionally, other non-medical factors may also contribute to China's decision to not use RATs on a large scale, said Chi. "Since RATs are mostly carried out by citizens at home, authorities in China may have less trust in the results of those tests," he told DW.

In an interview with China's state-run China News Weekly, Bo-lin Tang, the sales director of Ningbo Dasky Life Science, said that one of the reasons why RATs are developing slowly in China is because there is almost no market for rapid tests. "Since PCR tests are viewed as the gold standard in China and the country's testing capacity can keep up with it, there is no room for rapid antigen tests,” he said.

Additionally, since China's National Medical Products Administration (NMPA) uses a lengthy process to review COVID-19 test kits, Tang said manufacturers may find it troublesome to go through the official process and get the certificate issued by China's NMPA.

Combining the strength of RAT and PCR tests

One solution that combines the benefits of both the RAT and PCR tests may be on the horizon for Chinese citizens. In a peer-reviewed study published in the journal Nature Biomedical Engineering on Monday, Chinese scientists from Shanghai's Fudan University said they have developed a COVID-19 test that can process results as accurately as PCR tests in less than four minutes.

The researchers collected nasal samples from 33 PCR-positive COVID-19 patients, 23 PCR-negative patients, six influenza-positive patients, and 25 healthy volunteers. The test accurately processed all cases without error in under four minutes, according to the study. But since the study was conducted on a small sample, Johns Hopkins University's expert Andrew Ching told DW that it will only make a difference if the 100% accuracy rate can hold up in a larger test sample.

For the time being, Chunhuei Chi thinks that RATs may not gain the trust of the Chinese authorities anytime soon.

"Assuming that China will slowly consider moving away from the zero-COVID strategy after the major political event this fall, RATs may start to be taken more seriously by Chinese authorities by then," he said.

Chen from Yale also thinks that China's manufacturing capacity for RATs may play a more important role in its future pandemic-control measures. "The large manufacturing capacity for antigen tests will become more important as the zero-COVID strategy eventually shifts," he said.

Edited by: Leah Carter