Renowned Sri Lankan virologist Professor Malik Peiris said rapid antigen tests would be satisfactory when trying to control the COVID-19 transmission and identify the patients who are most infectious. Professor Peiris, the Chair of Virology at the Division of Public Health Laboratory Sciences of the University of Hong Kong, expressed these views at a recent briefing organised by the Ceylon College of Physicians and attended by Dr. Ananda Wijewickrama and Dr. Shamila De Silva. Explaining the function of rapid antigen tests, Prof. Peiris said, “When you are trying to control the transmission and trying to identify people who are most infectious, the rapid antigen tests would be satisfactory because that test is rapid and also will pick up the most infectious patients.” He said the PCR tests have the higher sensitivity but added that not every PCR positive case meant that the person is having infectious virus. “Since the antigen test is somewhat less sensitive than PCR, it picks up those patients with high viral loads. Correlations of antigen test with infectiousness is much better. Some of the early versions of this rapid antigen tests were not good but the more recent ones, the ones approved by the World Health Organisation (WHO), are much better. We need to be able to use both of these for the right purposes,” Prof. Peiris said. He further said, “If you have a patient who is sick, then the PCR is the choice. If want to make a decision quick and the nearest PCR machine is miles away, the antigen test may give you a faster result. “PCR tests detects not the infectious virus particle but the virus genetic material. So the genetic material of the virus can remain quite a long time after the virus is no longer infectious. Because of that, the WHO has changed its recommendations and basically says that asymptomatic and mild patients, after 8 to 10 days, are not infectious. So when you have to do a PCR, the PCR maybe positive but that does not necessarily means that the patient is infectious. On the other hand, antigen tests will identify the most infectious patients,” he said.