Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (479 page)

   There is a high rate of fetal loss or stillbirth. Fetal hydrops may be apparent.

   Most neonates are asymptomatic at birth but may show stigmata of infection, including skin lesions (including the palms, soles, and mucous membranes), hepatosplenomegaly, jaundice, and anemia. Radiographic abnormalities may be seen (e.g., periostitis).

   Untreated, damage cause by congenital syphilis may manifest by the Hutchinson triad (abnormal upper incisors, interstitial keratitis, 8th nerve deafness), as well as such conditions as frontal bossing, saddle nose, and high arched palate.

   Laboratory Findings

Direct microscopic detection
: Direct detection techniques may be used on exudates of active cutaneous or genital specimens during the primary or secondary phases of disease.

   
Dark-field microscopy
: Dark-field microscopy may be used to detect typical organisms; specimens must be examined immediately by an experienced microscopist. Documentation of the characteristic morphology and motility of organisms is critical. Dark-field microscopy should not be performed on oral lesions because of the presence of nonpathogenic, endogenous spirochetal flora.

   
DFA for T. pallidum (DFA-TP)
:

   This test is performed on exudate from chancres. Antibody reagent is used to detect
T. pallidum
in the material. Advantages of DFA-TP are that viable organisms are not required; immediate examination is not necessary. DFA-TP may be positive on chancre exudate in the first week, before a serologic reaction has occurred.

   The use of polyclonal antibody reagents may limit the utility of DFA testing if they are not preabsorbed (e.g., Reiter treponemes) to eliminate binding to antigens common to nonpathogenic treponemes.

   
Histopathology
: Tissue sections stained using a silver stain, or other technique for spirochetes, may demonstrate organisms and may provide support for diagnosis in immunocompromised patients who do not mount an antibody response to infection.

   
Serology
: Detectable antibodies develop during primary infection and increase in titer during the secondary phase of syphilis. Titers decline during the latent phase. The interpretation of serologic testing of neonates may be complicated by the presence of transplacental maternal antibodies. See Syphilis Serology Tests in Chapter
17
, Infectious Disease Assays for information about these tests.

   Non-Treponemal tests

   The VDRL-CSF assay is the only nontreponemal assay for detection of antibodies in CSF. VDRL on CSF is highly specific but lacks sensitivity (40–60%); therefore, it should be used to rule in, but not rule out, neurosyphilis. The VDRL-CSF cannot be used to follow response to therapy.