Evaluation of specific antibodies for early diagnosis and management of syphilis

Abstract

For many years, tests for cardiolipin antibodies Tp15, Tp17, Tp45, Tp47, and other specific Treponema pallidum antibodies, have been used to diagnose syphilis, but the timing and rates of antibody detection differ in primary and secondary syphilis. Our objective was to determine the value of the rapid plasma reagin (RPR) test, T. pallidum passive particle agglutination (TPPA) assay and Western blotting (WB) in the diagnosis of early syphilis, by studying 67 patients (20 with primary and 47 with secondary syphilis) over a recent 5-year period. All patients were tested before and 21/67 were tested after treatment. Western blotting showed that while there was a difference within the study group in terms of the number of bands detected, all patients with primary syphilis demonstrated the 47-kDa antibody, but RPR and TPPA were negative in some patients. Eighteen to 24 months after treatment, 21/67 patients were tested by WB and TPPA; antibodies to T. pallidum became undetectable within 24 months after treatment in 29% of patients. By RPR, 29% patients had negative titers within 6 months of treatment, and 86% returned to normal within 24 months. We conclude that detection of specific 47-kDa T. pallidum antibodies can be used to diagnose primary syphilis. By RPR, antibodies disappear in 6-24 months after treatment in many patients, suggesting that a change in titer may be an indicator of treatment success.