Comparison of Results given by a Complement-Fixation Test for Syphilis using the Reiter Treponeme as Antigen with the Treponemal Immobilization Test

Although the treponemal immobilization test (TPI) is now generally accepted as being a sensitive and highly specific test for treponemal disease, difficulties in its execution have restricted its performance to specialized laboratories. Alternative methods of demonstrating specific antibodies by agglutination, immune adherence, and complementfixation tests with virulent treponemes or extracts have been used, but as the yield of antigen from the testes of infected rabbits is relatively small, the use of these tests as routine serological procedures has not hitherto been practicable. The interest which the TPI and similar tests aroused has tended to distract attention from complement-fixation tests for syphilis which use suspensions of the Reiter trepomene as antigen. The serological properties of this organism, which can be grown in simple culture media, have been extensively investigated by the Italian group of workers led by D'Alessandro and Puccinelli, who have presented very favourable reports on its use in the serological diagnosis of syphilis. By the use of this organism, antibodies can be detected in syphilitic sera which are distinct from the reagin(s) whose presence is shown by the serum tests for syphilis (STS) using alcoholic extracts of tissue lipoids as antigens. Because of this, the Reiter antigen is thought to be more specific than the classical tests using lipoidal antigens. In this investigation, parallel tests have been carried out on sera with three STS: Wassermann reaction (WR) with a crude heart extract antigen, the Kahn test, and Price's precipitation reaction (PPR); a complement-fixation test using a suspension of the Reiter treponeme as antigen (RCFT); and the TPI test. Because of its high specificity, the latter has been used as the index for comparison between the other tests.