CAN WE RELIABLY DIAGNOSE SYPHILIS? Oral Presentation for 22nd IUSTI-Europe Conference On Sexually Transmitted Infections, 19-21 October 2006, Versailles, France

Objectives: To ascertain if syphilis screening reliably detects latent disease, including in the HIV context, by comparing standard syphilis testing with newly-developed techniques, using either recombinant antigen based treponemal serology or direct detection by DNA amplification.

Methods: (1) 500 patients at a downtown Toronto HIV clinic were screened from 1988-1992 with both RPR and quantified treponemal tests, including MHA-Tp (TPHA). (2) Serum aliquots from a further 250 patients from the University of Toronto's AIDS Epi-Study were similarly tested in 1992. (3) 557 patients from another downtown HIV/STD clinic were screened in 2000 as above, and also monitored with the Trep-Chek, a more sensitive, FDA-approved, recombinant ag-based EIA test. (4) Recently, 183 patients from two dermatology clinics in Budapest were tested for T. pallidum DNA with a nested PCR.

Results: (1) None of 500 patients were RPR(+), while 60/500 were TPHA (+), 11 of whom had no syphilis history. Six with a syphilis history were TPHA (-) with CD4 < 80/ul. (2) Of 125/250 Epi-Study patients with HIV, 24 had dropping treponemal titres during B-cell polyclonal activation, while only one HIV(-) case lost treponemal antibody selectively in this way. (3) Of 557 clinic patients, none were RPR(+), while 27 had evidence of syphilis by Trep-Chek, 24 of whom were WB (+) or equivocal. Nine were TPHA(+). Only 4/27 had ever been followed up. (4) 13/183 of the Budapest group were syphilis PCR(+), while only four had ever been treated. These four were the only TPHA (+) persons in the group.

Conclusions: Diagnostically, early acute syphilis is one thing and latent syphilis is quite another. RPR(+) findings were extremely rare among these nearly 1500 high-risk patients. Screening for syphilis with anti-lipoidal tests, based on a 1906 concept, is inappropriate. The persistence of treponemal antibody may indicate ongoing syphilis infection despite therapy, and such patients may need re-treatment and follow-up using gene amplification. Some patients with latent syphilis seem to have little or no treponemal antibody. It is therefore unclear to what extent undetected latent syphilis overlaps with HIV, and HIV/AIDS.