Laboratory Diagnosis of Syphilis

Dark field microscopy (DFM) is the only test that allows immediate diagnosis, treatment, and partner notification, thereby preventing further transmission. A highly positive IgM titer indicates, independently from the value of IgG or TPHA titer, an active infection and the need for treatment. A low IgM titer, in combination with a high IgG or TPHA titer, is consistent with a latent or chronic treponemal infection. A nega­tive IgM test, in combination with a high ­positive IgG or TPHA titer and a positive nontreponemal test, is consistent with an active infection as well.