[Serological tests should be related to the aim of the testing, as well as the population]

Expectations are high on serological tests for SARS-CoV-2. Further knowledge of the immunity is needed, but also evaluation of the reliability of the tests. Important for the latter is for which purpose the test is conducted and how common the outcome to be identified is (antibodies). For the determination of immunity at the individual level, the specificity of the test must be very high, preferably 100%. Even tests where the specificity is perceived as high, e.g. 95% or 99%, can lead to a large proportion of false positives, if the proportion of the population actually infected is small.