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Health authorities believe the samples are more accurate than previously thought.
On Monday, the NRK Folkeopplysningen program addressed the topic of safety tests on people suspected of being healthy.
The show was filmed before the pandemic and is not about covid-19, but proving inaccuracies in the testing methods can lead to many people being misdiagnosed.
For example, if a test method is 99 percent safe, 1 in 100 people tested will get an incorrect answer.
Also read: Trump adviser rejects hopes of a vaccine before the elections: – Unlikely
FHI has warned against incorrect corona responses
In May, the National Institute of Public Health issued a press release actively warning against testing large groups of healthy people in a low-infection setting.
Given the current infection situation in Norway, health professionals must test about 12,000 random people to find a positive case with COVID-19. In such a sample, there will be about 15 positive results, but 14 of these will be false positives, said Dr. Joakim Øverbø of the National Institute of Public Health.
The estimate was based on the test being less than 99.9 percent certain.
Test activity has increased significantly, as has the number of tests.
Since then, testing activity has increased significantly in Norway. People can decide for themselves if they want to be tested and, broadly speaking, we now test as many people daily as we did for a week at the start of the pandemic.
Also read: NIPH on rising infection rates: – It’s too early to tell if this is a trend
The increase in test activity is followed by a sharp increase in the number of registered infected.
The number of new infections in Norway has grown considerably during the peak testing period.
Photo: (FHI)
Think that false positives are much less of a problem than previously thought
Both the National Institute of Public Health and the Norwegian Health Directorate now deny Nettavisen that the main reason for the growth is that more tests give more false positive responses.
– The PCR test for SARS-CoV-2 has a very high sensitivity if taken correctly. Specificity (precision) is also extremely high, close to 100 percent, because a positive response requires genetic material from the virus tested by PCR, writes assistant health director Espen Rostrup Nakstad in an email to Nettavisen.
– With the correct test indication, it is therefore very rare to get false positive test results, but of course it can happen due to technical conditions in the laboratory, he notes.
Dr Joakim Øvrebø from the Norwegian Directorate of Health says the test proved to be more accurate than expected in May:
– Based on updated information and preparation of very good routines for sars-cov-2 PCR in Norwegian laboratories, we consider that the PCR methods for sars-cov-2 used in Norway today are very specific. What we are saying is that he rarely gives false positive answers, Øvrebø writes in an email.
– Our best estimate now is that the method probably has a specificity of around 99.999 percent. That is, if 100,000 Covid-19 negatives are tested, probably 1 will be positive (false positive). At week 35, 84,554 people were tested and 374 tested positive. With a specificity of 99.999 percent, a maximum of 1 out of 374 will likely be false positives, Øvrebø says.
Also read: So many infected people think that FHI is in Norway now, and they live here
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