Reliability of the cut-off value in the routine serodiagnosis of pertussis performed by the commercial ELISA assays

A simple publication describing the validation study of serologic testing for pertussis used in a large national investigation of pertussis. The diagnosis of pertussis was problematic at that time, since all commercially available tests were unreliable. Many reference laboratories elaborated their own ("in house") tests containing known antigens. However, the Polish reference laboratory at the National Institute of Hygiene in Warsaw, was still using commercial tests, as it was important for accreditation. In this validation study, the reference laboratory tried to estabilsh a valid threshold for their test, that would discriminate truly positive from truly negative results.