The Hong Kong government has decided to adopt the same interpretation of Covid-19 PCR test results as the mainland, meaning people with a low viral load will be deemed not to have the virus at all.

In a statement, authorities said that from Monday, any PCR test result with a Ct value of 35 or above will be defined as negative. A higher Ct value indicates a lower viral load.

Health officials said in light of the new definition, people who have a Ct value of 35 or higher will not be required to undergo isolation, adding that this policy will help society return to normal.

The Centre for Health Protection said the change is being made in view of the fact that many people with a low viral load are unlikely to spread Covid.

People already in isolation who find themselves deemed uninfected under the new policy will be told by text message that they can go out again.

But since rapid antigen tests do not indicate Ct values and are less sensitive than PCR tests, anyone found to be positive via a RAT still has to report their infection to the authorities and isolate at home or at a government facility.

A spokesman also reminded people who plan to travel to the mainland that they have to pay for a PCR test in the 48 hours before their trip, and anyone with a Ct value lower than 35 will not be allowed to cross the border.

Ricky Chiu, who runs several testing centres in Hong Kong and is also an adjunct associate professor at the CUHK School of Biomedical Sciences, said the change in interpreting test results is sensible and reasonable.

He said it will not increase the time it takes for labs to send out results, and nor will it add to the workload or operating costs of the laboratories.

“Everything’s being automated. Simply we are changing the standard where the test results are deemed positive or negative. If you think about that, actually, our workload is less because before, any positive results we need to do a double check, a triple check, to ensure the result is a true positive result before we give the report back to the citizen or the government,” he explained.

“But now, since anything that is 35 or above we can consider that as negative, and that will reduce the workload in the lab,” he said.

Chiu said the new standard will make life easier for people who want to travel to the mainland.

There have been media reports that people who recently recovered from Covid could not cross the border because PCR tests showed they still had a low viral load.