'Airport Covid Tests Can Miss A Quarter Of Cases'

Polytechnic University researchers said on Monday that Covid-19 tests at the airport could miss at least a quarter of imported infections because of what could be "false negative" results.

The team, which studied virus strains found in Hong Kong, said of the 286 imported cases in the city between September and October, at least 25 percent of the patients were only confirmed when they were being quarantined at hotels or at home.

Gilman Siu, from the University's Department of Health Technology and Informatics, said routine testing at the airport was unable to identify patients with low amounts of coronavirus in their bodies, especially in their first few days of infection.

"The viral load in the patients somehow would be too low... very difficult to be detected by the routine test," he told a virtual news conference.

Siu noted that the test is unable to pick up patients with a viral load of less than 250 copies per millilitre.

The real-time RT-PCR nucleic acid tests are supposed to yield results that are more accurate than a recently introduced rapid test at the airport.

Siu said he's surprised by the "worryingly" high percentage of false negatives of the routine tests.

And with the pandemic still raging, he's concerned that incoming passengers could spark the fourth wave of infections.

Siu noted there's a loophole in quarantine measures, in that family and friends are allowed to visit people undergoing mandatory quarantine. He believes that's one of the reasons behind the spread of cases in the community in recent months.

He said during a recent visit to a hotel which had seen a number of confirmed Covid cases, he could enter freely without anyone stopping him.

"I just pretended to visit my family... I [didn't] encounter any problems, I just go inside, nobody questions me, I could get into the elevator and to the hotel room and then go back," Siu said.

He urged the government to discuss with the hotel industry about having designated quarantine hotels, so that they could be guarded by health officials. Travellers should also use designated transport to head into quarantine.

Last updated: 2020-11-16 HKT 20:16