SOS International challenges SSI’s statement on antigen test

On 11 November, the Danish Statens Serum Institut (SSI) announced that antigen testing should only be used as a supplement to PCR testing. SOS International sees weaknesses in the French study on which SSI based this announcement.

In its announcement, SSI referred to a French study of antigen testing which indicates inter alia that the antigen test used by SOS International has a sensitivity rate of 59.6 %. The manufacturer and distributor states that the test has a sensitivity rate of 96 %.

A close reading of the French study to which SSI referred reveals the following problematic information:

• The test method used in the study differs from the method prescribed by the manufacturer. The analysis is based on samples collected in spring and frozen to minus 80 degrees. The use of frozen samples from the nasal cavity swabs constitutes a significant source of error.

• The authors of the French study very carefully list the limitations of the study. These limitations were not reproduced by SSI.

• In October, SOS International's own test data showed a positive rate of 1.5 %. This is in line with the positive rate at TestCenter Denmark at the time. This would not be statistically possible if our antigen tests were as inaccurate as assumed by SSI as SOS International performs tests on asymptomatic individuals.

SOS International agrees that it is important to use tests that are valid and credible. Until SSI provides evidence that the limitations and sources of error that may exist in the French study do not affect its conclusion, SOS International will refer to the information on the antigen test provided by Apodan (distributor) and Biosynex (manufacturer), respectively: The Biosynex antigen test has a sensitivity rate of 96 % and a specificity rate of 100 %

Moreover, SOS International believes that SSI needs to take the behavioural factor into account when comparing tests performed by TestCenter Denmark and antigen tests: Individuals ought to self-isolate in the period prior to having the test, again after the test and until they receive their test results. If they do not comply with this, everything speaks in favour of an antigen test that provides an answer immediately.

SOS International further notes that, as of 9 November, the Norwegian authorities accept antigen tests on an equal footing with PCR tests on entry into Norway.