Until now only non-treponemal tests (e.g. rapid plasma
reagin [RPR]) have been used to monitor
syphilis activity (e.g. distinguishing between treated, untreated and repeat disease) and efficacy of treatment. However, they usually require manual operation and are less specific than treponemal tests. The aim of the current study was to evaluate the use of the antitreponemal
IgM testing in the diagnosis of early and repeat
syphilis in HIV-infected and non-infected patients. One hundred and seventeen patients with early
syphilis were included in this prospective study. RPR and anti- Treponema pallidum-
IgM (TP-
IgM) tests were conducted at onset and at three-month intervals during 24-month follow-up after initial treatment. In 31 of 117 syphilitic patients the co-occurrence of
HIV infection was diagnosed. A positive TP-
IgM test was present in 78.6% of patients with newly-diagnosed
primary syphilis, 95.8% with secondary and 57.9% with early
latent syphilis, but only in 38.5% patients with
syphilis reinfection. There was a significant correlation between primary and
secondary syphilis, higher baseline RPR titre and the pre-treatment
IgM test reactivity. Regardless of the
syphilis stage, HIV-seropositive individuals were more frequently positive for TP-
IgM, both during the first onset of the disease (90.3%), and
reinfection (71.4%), as compared to the HIV-seronegative group (71.4% and 0%, respectively, P < 0.03). TP-
IgM seroreversion was observed in 115 out of 117 patients studied (98.3%) during follow-up (mean time to seroreversion 6.9 months). The time to TP-
IgM seroreversion
after treatment was significantly shorter in patients with early symptomatic
syphilis (mean 4.9 months) when compared to early
latent syphilis (7.7 months, P < 0.05). A negative TP-
IgM test was found in approximately 20% and 40% of individuals with primary and early
latent syphilis, respectively. The value of
IgM testing in the diagnosis of
syphilis reinfection is doubtful.