This article examines the reliability of IgA and IgG antibody levels considered diagnostically significant in ELISA tests for pertussis. The authors compared cut-off values established by the manufacturers of two popular ELISA kits (NovaTec and Virotech) with values calculated based on studies of healthy children and adults in Poland. They found that the cut-off level for IgG antibodies in the NovaTec kit is more than three times lower than the actual level, leading to false positive results in many healthy individuals. In the case of the Virotech kit, the cut-off values were closer to the actual values. The authors suggest that commercial ELISA tests require further improvement and standardization to ensure more reliable results.
This investigation was an important component of our national study on pertussis incidence. At the time, pertussis diagnosis was challenging because commercially available tests were unreliable. As a result, many reference laboratories developed their own in‑house assays using well‑characterized antigens. The Polish reference laboratory at the National Institute of Hygiene in Warsaw, however, continued to use commercial tests to meet accreditation requirements. This validation study therefore aimed to establish an appropriate diagnostic threshold that would reliably distinguish true positive from true negative results.