The clinical value of the Treponema immobilization test in the diagnosis and control of syphilis.

Ever since the first report of the Wassermann reaction in 1906 the physician has often been faced with the problem of correctly interpreting and coordinating with the clinical findings the results of various standard serological tests for syphilis. Improvements in the methods and materials, particularly the purification of the antigen in the form of cardio'ipin, have not completely eliminated the false positive reactions that are sometimes given by both complement fixation and flocculation tests. This is not surprising in view of the fact that all these tests are based on an empirical reaction between a non-specific antigen consisting of a lipoidal tissue extract and a so-called antibody in syphilitic serum called reagin. Attempts to grow virulent Treponema pallidum in artificial culture medium and thereby provide sufficient specific antigen for serological tests have hitherto failed. However, a new approach to the problem was made when Nelson and Mayer (1949) devised the Treponema pallidum immobilization (T.P.I.) test for syphilis. Virulent T. pallida were extracted from infected rabbit testes into a special anaerobic medium in which they were kept alive and virulent for several days. This relatively tissuefree suspension of mobile T. pallida was immobilized when mixed with syphilitic serum in vitro in the presence of active complement. No such immobilizing effect was obtained with normal or serologically false positive sera or in the absence of fresh complement. Since a virulent strain of T. pallidum (Nichols' strain) was used, the T.P.I. test was considered a specific test for syphilis involving a specific anti-treponemal antibody. This antibody was demonstrated to be distinct from the Wassermann antibody which could be absorbed from the syphilitic serum with lipoidal tissue extract antigen leaving the immobilizing antitreponemal antibody intact. In the present study 532 specimens of blood sera and 56 of cerebrospinal fluid from syphilitic and non-syphilitic persons have been examined with four tests in parallel, namely the T.P.I. test, the Wassermann test, the Kahn test, and the Venereal Diseases Reference Laboratory (U.S. Public Health Service) (V.D.R.L.) slide flocculation test. The results obtained confirm in general the findings of earlier workers (Nelson and Mayer, 1949; Nelson, Zheutlin, Diesendruck, and Austin, 1950; Nelson and Diesendruck, 1951; Magnuson and Thompson, 1949; Mohr, Moore, Nelson, and Hill, 1950; Durel, Sausse, Collart, Roiron, and Borel, 1951) so far as the specificity and sensitivity of the T.P.I. test in the diagnosis of syphilis is concerned. From the results obtained the practical value of the T.P.I. test to venereologists in this country is assessed.