Treponema pallidum agglutination tests.
One approach to obviating some of the difficulties and complexities of the Treponema pallidum immobilization (TPI) test is to be found in the use of T. pallidum as an antigen in agglutination tests. The four main representative techniques of such tests are compared with respect to: strain of organism used, treatment of rabbits, time of harvesting, extracting medium, method of inactivation, preservative, and reagent. The results obtained with the different techniques are then reviewed and the various difficulties met in each are discussed.The authors consider that the T. pallidum agglutination tests do not yet have a diagnostic value equal to that of the TPI test; the technical difficulties have not yet been overcome, and the immunological interpretation of results is by no means clear. Much still has to be done, and indeed it is possible that entirely different methods may even supersede techniques using whole, virulent T. pallidum as antigen.