Different sampling methods show inconsistent COVID-19 test results in 25 cases at HK airport


22nd November 2020 – (Hong Kong) The Hong Kong government used gargle samples as a sampling method to conduct RT-LAMP nucleic acid detection technology at the airport earlier, and also used deep throat saliva samples for RT-PCR nucleic acid detection to make comparisons and test the sensitivity and reliability of the technology.

The Food and Health Bureau announced yesterday (21st) that there have been discrepancies in the test results of 25 cases so far. The relevant tests lasted for 3 weeks and ended on the 17th of this month. Regarding the different results in the airport test, the Food and Health Bureau stated that six of the cases tested negative in deep throat saliva samples at the temporary sample collection centre of the Department of Health at the airport, and the participating institutions tested the separately collected mouthwash samples. The results were positive, negative, or unconfirmed. Among them, 4 deep throat saliva samples were also positive when reviewed by the Department of Health. During the test, there were other cases where the mouthwash samples tested by the participating testing institutions were negative, while the Department of Health tested positive for deep throat saliva samples. The detailed results need to be evaluated after analysing the test data. At this stage, the government has no conclusion on the test.

The Food and Health Bureau emphasised that all relevant passengers who have been reviewed as confirmed cases have been sent to hospital for isolation in accordance with established procedures, and stated that the various detection techniques and sampling methods used for COVID-19 test have their advantages and limitations and adopt different tests. It is not uncommon for techniques or sampling methods to give different results.