Singapore said Thursday it will stop using polymerase chain reaction test as a criteria for releasing COVID-19 patients and will now adopt a time-based discharge policy, allowing such patients to go home after just 21 days of isolation.

"With immediate effect, all COVID-19 patients who are assessed to be clinically well by Day 21 of onset of illness can be discharged without the need for further PCR tests," the Health Ministry said in a statement.

A cyclist rides past a worker wearing protective mask cordoning off the Merlion Park with tape on May 26, 2020 in Singapore. (Getty/Kyodo)

The decision is based on new scientific evidence that the virus fades away after the second week from the onset of illness "despite the persistence of polymerase chain reaction detection of ribonucleic acid."

The World Health Organization has also recommended the adoption of a time-based discharge criteria.

Singapore decided to continue to isolate all patients until the end of the third week as an extra precaution, it said.

They will have to remain in their residence for a further seven days after being discharged to rest and recover and can return to work after the 28th day.

"What we are going to do now is to reduce the number of tests we need to do for the purposes of clearing patients from our hospitals and community care facilities to return home," said Kenneth Mak, the ministry's director of medical services.

Singapore, which has been aggressive in conducting tests for COVID-19 cases, with more 330,000 tests so far, or more than 58,000 tests per 1 million population, plans to continue to do so to detect new infections in migrant workers dorms.

Health Minister Gan Kim Yong told reporters that with this change in policy, "There will be a group of patients who have been with us for a long time, some maybe 50 days, more than 50 days. Some of these patients actually ought to be at home because they are no longer infectious."

The move comes at a time when Singapore is about to gradually lift its two-month-long semi-lockdown from June 2 amid signs that community transmission has been kept under control.

On Thursday, 373 new infection cases were reported, bringing the total to 32,876, with 23 deaths. Of the total 510 were in hospitals and 14,422 isolated and cared for at community facilities.