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Diagnostic Methods
History
Obtaining a detailed history is critical for determining the duration of infection and assessing the possibility of reinfection. When obtaining the patient’s history, the health care professional should assess whether the patient has had:
- A history of syphilis (if yes, obtain results of previous serologic tests for comparison purposes).
- Known contact to an early case of syphilis.
- Typical signs or symptoms of syphilis in the past 12 months.
The health care professional should also determine the date and results of patient’s most recent serologic test for syphilis, even if the patient reports no history of the disease. This is particularly helpful for evaluating a patient with a low titer serologic test, no symptoms or symptom history, and no known contact to an early case of syphilis.
The local health department may be able to provide information on whether the patient has been reported as having had syphilis in the past, including reported serologic test results.
Physical Examination
A thorough exam includes checking the oral cavity, lymph nodes, skin of torso, palms and soles, and the genitalia and perianal area for signs of infection. A pelvic examination should be conducted on female patients. A neurologic exam should be completed that concentrates on cranial nerves including II (optic), III (oculomotor), VI, VII (facial), and VIII (auditory).
An abdnominal exam should be performed for liver tenderness.
Laboratory
The definitive methods for diagnosing early syphilis are darkfield microscopy and direct fluorescent antibody tests of lesion exudate or tissue.
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Darkfield microscopy
T. pallidum cannot be viewed by normal light
microscopy. Darkfield microscopy can identify T. pallidum with its spiral shape, 10-14 coils, corkscrew motion, and a total length of 6-20 micrometers.
Advantages of darkfield microscopy:
- Definitive immediate diagnosis (useful in primary and secondary disease).
- Rapid results.
Disadvantages of darkfield microscopy:
- An experienced microscopist and specialized equipment (often not available outside of a specialized clinic)
are required.
- Confusion with other pathogenic or nonpathogenic spirochetes may occur. Generally not recommended on oral lesions because of
specificity problem with nonpathogenic spirochetes in the oral cavity.
- It must be performed immediately because motility is important to identification. The
sensitivity of darkfield microscopy decreases as the lesion heals.
- Possibility of false-negatives increases with use of topical substances such as soap and water, antibiotic ointments, etc.
Direct fluorescent antibody
Direct fluorescent antibody - T. pallidum (DFA-TP) identifies T. pallidum on direct lesion smear by immunofluorescence using polyclonal antiserum
or monoclonal antibody.
Advantages of DFA-TP:
- Polyclonal reagent is absorbed to remove most
cross-reactive antibody.
- Compares favorably with darkfield microscopy.
The disadvantage is that the turnaround time is 1-2 days, so it requires the patient to return.
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