The Treponema pallidum Complement-Fixation Test

Abstract

Results of tests with lipid antigens (standard serologic tests; STS), Treponema pallidum immobilization (TPI), and Treponema pallidum complement fixation (TPCF) tests on 395 patients with treated and untreated syphilis of various stages show agreement among TPI and TPCF to be 87.3%. The TPCF is more sensitive in early syphilis; the earlier appearance of the antibody involved in this test can be experimentally shown. In 266 patients with biologic false positive reactions or latent syphilis, STS, TPI and TPCF results agreed only 33.5% of the time, while TPI and TPCF results were in agreement 94% of the time. When results of tests on treated and untreated patients were considered separately, it was found that in the early stages of syphilis the TPCF results in untreated cases paralleled the STS results, while in the later stages TPCF and TPI results showed the higher correlation. In the treated group, tests on early cases showed a somewhat greater correlation between TPI and TPCF than between either of these and STS results. The correlation between TPI and TPCF results was somewhat less in the treated, late group than in the treated, early group. A brief discussion of the limitations of serologic tests, with respect to the variety of antibodies evoked in syphilis, is included.