With that said they had to retract the test results but that was due to other reason (accidentally including people who gave blood due to being infected).
Google Translate:
> Karolinska University Hospital and Karolinska Institutet have collaborated to produce a new antibody test in the fight against covid-19.
> - We are happy to have a test that we know is okay. It is not 100 percent sensitive, it has sensitivity of 70-80 percent. Some will test negative even though they have had it. But no one will test false positively. Those we have tested that should be negative have been, says Jan Albert.
(Google Translate translates chief physician to consultant for some reason but other than that the translation seems fine)
If a test has a 100% specificity, and you give it a sample that has been contaminated with the virus, the fact that it registers a positive result is not an error.