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The Number of Nucleic Acid Testing Agencies in Beijing Increases to 124

2020/06/22

At the press conference on Beijing's COVID-19 response held on 21 June, spokesperson of the Beijing Municipal Health Commission Gao Xiaojun gave a briefing on Beijing's efforts to rapidly expand the city's nucleic acid testing capacity since COVID-19 cases emerged in the Xinfadi Wholesale Market on 11 June. As of 20 June, the number of nucleic acid testing agencies in Beijing increased to 124, with the maximum daily capacity increasing to 230,000 tests. Among these agencies,20 are centers for disease prevention and control; 73 are tier-two and tier-three hospitals, and 31 are medical laboratories. The city would be able to process around one million samples per day if 5 samples are pooled together and tested in a small batch.

【Questions Raised at the Press Briefing】

1. If close contacts of confirmed cases have been tested negative in their first NAT, do they still need to be placed under quarantine?

According to Li Jinming, a researcher at the National Center for Clinical Laboratories, close contacts of COVID-19 cases need to be placed under quarantine even if they have been tested negative in the first NAT, because close contacts have a much higher risk of contracting the virus than others. During the quarantine, should the person develop symptoms, he or she will need to take another NAT. Even if the person shows no symptoms during the quarantine, he or she will still need to take another NAT and if tested negative the quarantine can be lifted.

2. Are false negative results avoidable?

Researcher Li Jinming at the National Center for Clinical Laboratories said that false negative results cannot be ruled out completely due to factors that may affect accuracy, such as the timing of sampling, types of samples and lab testing operation.

A positive NAT result is usually the golden rule for detecting a virus infection, but there can be false positives, for example when a sample has already been contaminated before. False positive can be avoided through re-testing.

There is always a possibility of a false negative result. Take timing of sampling as an example. False negatives may happen to a close contact when samples are taken at the beginning of an infection, or in the case of long incubation. It may also happen at the late stage of incubation period or at the time of early symptoms. Incorrect operation of collecting a sample or mutation of the virus may also lead to testing inaccuracy.

(Full Text is Available at http://bjrb.bjd.com.cn/html/2020-06/22/content_12467891.htm)

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