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Since the beginning of the pandemic, so-called PCR tests have been standard in Sweden. These are tests that show an ongoing covid-19 infection and are analyzed in a laboratory.
Some steps in the process are time-consuming and resource-intensive, so individuals have had to wait several days for test results as testing has reached new record levels.
The faster it is possible to get a response to the so-called antigen test. In half an hour, there is a positive or negative response according to the World Health Organization, WHO, which this week announced that 120 million antigen tests will be distributed to low- and middle-income countries.
Soon they may also be relevant in Sweden.
– We see that they can have great potential, but as with PCR tests, they need to be introduced in an orderly manner, says Karin Tegmark Wisell, head of department at the Swedish Public Health Agency.
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She continues:
– There are limited clinical studies and large-scale testing experiences at this time, but new results and publications are coming very close, so we are working to produce a guide that clarifies how we approach antigen testing.
Karin Tegmark Wisell sees that there may be areas of use for antigen testing. Photo: Janerik Henriksson / TT
Less sensitive antigen tests
Speed is considered the great advantage of antigen testing, although it is cheaper than PCR testing. But there are also downsides.
– They have slightly different sensitivities, so antigen tests can’t really show the same low virus levels as PCR tests, says Karin Tegmark Wisell.
Facts: differences between corona tests
Karin Tegmark Wisell explains which components of the new coronavirus are found in ongoing infection tests:
“PCR tester it detects the genetic material, the genome. “
“Antigensternal it detects proteins, the very structure that makes up the virus.
The tests should not be confused with antibody tests, which are used to see if a person has been previously infected.
So-called specificity, the probability that the test result will be false positive or negative, is also slightly worse with antigen tests.
The Swedish Public Health Agency still sees that there may be areas of use for antigen testing.
– We see that they can play a role in certain situations, especially in a situation with a wide spread of the infection. But we think there is still a bit of knowledge before I recommend them widely on our part.
READ MORE: Health centers are now starting antibody testing: 10,000 samples per week expected in Sahlgrenska
Taken with a stick to the nose
The sample itself is taken with a stick in the nose, but although several regions now offer PCR tests as self-tests, it is not possible with antigen tests.
– They have taken longer to develop and therefore, so far, from what we have seen, they are adapted for tests carried out by health and medical personnel.
India is one of the countries that has already started antigen testing to increase testing capacity. Image: Manish Swarup
It has not been decided exactly in which situations antigen testing can replace PCR testing, but Karin Tegmark Wisell sees reasons to gradually start introducing antigen testing in Sweden.
– At the moment, there can be many reasons to test and validate and see potential areas of use under controlled forms, where you also run alternative tests to verify that nothing is lost.
READ MORE: Incorrect test results analyzed – significantly less infected after control
PCR is still the main rule
Last week, Swedish researchers published a study showing how corona tests can be faster.
It was about being able to skip certain steps in the analysis of PCR tests, something that is already being done in several Swedish laboratories, according to Karin Tegmark Wisell.
– So it’s not really a breakthrough, but on the other hand it’s important to publish what you see is possible. We still see PCR as the “gold standard” for detecting the presence of the virus.
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