Clinical and diagnostic issues of acquired and congenital syphilis encompassed in the current syphilis epidemic

The current epidemic of syphilis has served to focus renewed attention on the clinical complexities of the disease as well as limitations in methods for its diagnosis. As serologic screening efforts for identifying active disease intensify in response to the syphilis epidemic, new studies show that titers of nontreponemal tests for syphilis (eg, Venereal Disease Research Laboratory or rapid plasma reagin) posttherapy do not decline as rapidly as previously asserted, although levels in patients with low initial titers or first infection episodes appear to decline more rapidly than those of repeat infections or later stages of the disease. After therapy, seroreversion of treponemal tests for syphilis (eg, microhemagglutination assay for antibodies to Treponema pallidum or fluorescent treponemal antibody-absorbed test) can also be as high as 13% to 24% in patients with first-episode primary syphilis. In patients coinfected with T. pallidum and human immunodeficiency virus, there is increasing evidence that nonreactive treponemal or nontreponemal serologic tests may not exclude past or present syphilis infection. Enzyme immunoassay is being exploited in new serologic tests for syphilis, with assays for IgG reportedly having high sensitivity and specificity, although some studies revealed lower sensitivity and positive predictive value when used as a serologic screening assay; cross reactivity with antigens of Borrelia burgdorferi also were reported. Immunoblotting (Western blotting) has also been employed with high sensitivity and specificity (compared with the double-staining fluorescent treponemal antibody-absorbed test) to detect IgG specific for T. pallidum in the serologic diagnosis of acquired syphilis. With the inability to culture T. pallidum, the polymerase chain reaction continues to hold promise as a surrogate marker for treponemal infection through the detection of T. pallidum DNA in tissues and body fluids. New diagnostic approaches to facilitate the diagnosis of congenital syphilis, particularly in asymptomatic infants born to mothers with suspected active disease, include the combined use of immunoblotting for neonatal serum IgM as well as polymerase chain reaction for the detection of treponemal DNA in amniotic fluid and neonatal blood, serum and cerebrospinal fluid. However, the recognition that mothers with incubating or primary syphilis and their infants may present with nonreactive maternal or neonatal serologic tests for syphilis at the time of delivery, and the reemergence of congenital syphilis in areas where cases previously were rare, underscore the need for improved diagnostic methods and renewed attention towards the diagnostic dilemma of both acquired and congenital syphilis.