PCR versus Antigen testing – can they effectively fight the Covid-19 virus? | Sunday Observer

PCR versus Antigen testing – can they effectively fight the Covid-19 virus?

8 November, 2020

In the past one month, controversy over two comparatively recent tests- namely Polymerase chain reaction test (PCR) and Rapid Antigen testing which have been given the green light by the World Health Organisation to be used on Covid-19 victims and potential victims has been mounting . Now with reports that a large number of the Rapid Antigen test kits had already arrived in the country, it has further opened a hornet’s nest with many arguing for and against the tests.

To get more insight into what these tests were, why they were so important at this time around when the number of Covid-19 patients were on a sharp upward curve, and their benefits to the nation as a whole, the Sunday Observer spoke to two eminent health officials for their views.

Deputy Director Health Services, Ministry of Health, Dr Hemantha Herath taking time off his busy schedule said in a telephone interview, “ Both tests – the PCR and Antigen Rapid Testing , are equally useful and effective tests albeit each has its own differences and weaknesses.

After conducting several trials in different countries, the World Health Organisation which is the apex health organisation globally, has now recommended Antigen testing in a specific situation, basically to screen the people in a very short period of time. This test will cost only a fraction of a PCR test as there won’t be a need for laboratories and expensive equipment and can also be performed by trained field staff. Hence, that money can be used to solve some other useful health issue,” he said.


Responding to our query on how accurate they were he said, ´ “In the case of Rapid Antigen nasal swab tests, it is possible to do thousands of such tests in a short time. This test is useful when it is necessary to test a whole community and should be used as surveillance tests, a diagnostic test that determines if you are infected by analysing a sample to see if it contains genetic material from the virus. However, if a patient tests positive, the PCR test is more accurate although the time taken for it is much longer. It takes about 12 hours to do the entire sampling so the result will be available only the day after.” he said.

He added that getting Antigen testing test kits would not mean that PCR testing will be abandoned. “Both tests will be continued indefinitely till we find a vaccine for this virus”, he said.

Asked if he could tell us how many and from where the Antigen kits had been imported he said he couldn’t provide that information as it did not come under his purview and referred us to a technical expert for further information.

Rapid Antigen tests

Responding to our query as to how accurate the tests were, Director, Laboratory Services, Ministry of Health Dr Vijith Gunasekera set the picture straight at the outset when he told us, “To compare PCR and Rapid Antigen tests is like comparing apples and oranges. In the current health crisis, the PCR is still the gold standard for diagnosing Covid-19. Rapid tests and PCR go hand in hand. To say that the Antigen Rapid test will replace the PCR is a myth,” he said.

He said that while the Antigen Rapid test and PCR were both equally important, the difference was that the Rapid tests were more suitable when screening large high risk outbreak communities, but were not effective if the prevalence is very low in the community. Asked why, he explained that because the results were so quick it could give a false indication and thus a false sense of security to the people.

“That is why these tests should be used in the community, done only in special instances and carefully based on scientific epidemiological evidence”, he said. Noting that the Rapid Antigen test was a valuable tool in terms of public health he said, “the Ministry does these tests as a public health intervention to detect Covid-19 spread in the community rather than at individual level, and are important because they help to detect and assess the spread and the outbreak of Covid-19”.

Asked about the costs of the tests, he said a Rapid Antigen test would cost the government around Rs 1,200 but in community settings it would cost more .

A PCR test on the other hand would cost the government around Rs 6,000 but in the private sector the range would be between Rs 6,500 - 9,000 depending on whether home visits were included and cost of transport, etc.

On plans regarding the use of the newly arrived Rapid Antigen test kits, he said, the government was in the process of evaluating them. “If satisfied we will introduce them gradually into the health system. Asked if the quality was satisfactory, he said, “The products we are using have been recommended by the WHO and are of very high quality.”