Gonococcal serology. A comparison of three different tests

Three serological tests for the detection of gonococcal antibodies were compared: an enzyme-linked immunosorbent assay (ELISA), an indirect haemagglutination reaction (IHA), and a gonococcal complement-fixation test (GCFT). The ELISA was performed with gonococcal pili of a Rotterdam strain (1443) as antigen, the IHA with pilus antigen of an American strain (2686, Buchanan), and the GCFT with whole gonococci of a single strain (46695, Oliver) as antigen. The tests were performed on sera from the same groups of Dutch patients; samples of sera were taken at the first examination and generally 11-22 days later. The ELISA and the IHA were more sensitive than the GCFT. The specificity of the tests was equal in low-risk groups, but the GCFT was slightly more specific in high-risk groups. The ELISA and the IHA did not differ in sensitivity and specificity. The agreement between the ELISA and IHA for patients with uncomplicated gonorrhoea was low (chi = 0.44), but the agreement between the GCFT and the two pilus assays was less (chi = 0.26 and 0.20). The sensitivities were highest for sera from patients with oropharyngeal gonorrhoea or with gonococcal complications; again the ELISA and the IHA were more sensitive than the GCFT.