Why we must receive frequent, repeated nucleic acid tests

Imaginechina

Nucleic acid testing has become a key part of the daily life of Shanghai citizens.

Since the COVID-19 resurgence in early March, many locals have been accustomed to lining up with neighbors to receive polymerase chain reaction (PCR) testing.

Many citizens have questioned whether such repeated testing is necessary since they've tested negative multiple times.

Gao Chunfang, director of the testing laboratory center at Yueyang Hospital, responded at the city's daily COVID-19 press briefing on Sunday that the frequent testing is not only necessary, but also the "most effective and important way to put the pandemic under control."

"Such screening can help detect positive cases, especially the asymptomatic infections, as early as possible," Gao said. "It can also help to spot risky areas and groups to conduct control measures to block the spread of the pandemic."

The coronavirus has an incubation period, which varies in different people, and there is also a testing "window period" for the viral load to increase to high enough to be detected, which means an early infection might be missed during a single PCR testing, Gao explained.

Furthermore, the current sample collection measures, such as throat or nose swab or a combination of both could also produce "fake" negative result, depending on the depth of swabbing and the amount of secreta collected.

Under such circumstances, it is necessary to conduct multiple tests to detect positive cases.

For the infected, repeated testing can help to monitor the changes of the viral load, which can become a key reference on the effects of treatment and recovery.

Gao said repeated testing is actually a common clinical way to detect pathogens such as for urinary or blood tract infections. At least three tests are required to confirm a positive pathogen.