Abstract
Like all other sero-diagnostic tests the Reiter protein complement-fixation test for syphilis does not enjoy perfect specificity or sensitivity. Nonspecific reactive RPCF tests can in some cases be explained by the occurrence of antibody against the polysaccharide fraction of the Reiter treponeme. The prozone phenomenon may be responsible for non-reactive RPCF tests in syphilitic sera. For optimal accuracy the tests should be performed quantitatively. The quantitative RPCF test has excellent reproducibility under controlled standardized conditions.