Mini Guide for Diagnosis of Syphilis

Syphilis is a chronic infectious disease that presents with a range of symptoms depending on the stage of infection. It occurs all across the world and the incidence varies greatly depending on geography. The causal bacterium, Treponema pallidum was originally recognized in 1905 but serologic testing is the basis of laboratory diagnosis due to the organism's inability to be cultured and the limitations of direct microscopy.

There are various stages that make up the complete course of the disease. A chancre at the injection site designates the initial stage. A polymorphic rash, lymphadenopathy and other systemic symptoms are indicative of the secondary stage. There is an atypical latent period that can be classified into two stages: early (less than a year) and late (more than a year). Primary, secondary and early latent stages have the ability to be potentially infectious. The most damaging stage, known as the tertiary stage, is characterized by gummatous infiltration of all organ systems, cardiovascular and neurological aftereffects. Protean early or late symptoms can also arise from congenital infection.

It was necessary to develop alternate diagnostic techniques because there wasn’t a way to prove Treponema pallidum's presence through culture. Traditionally, there have been two categories for these techniques: serologic testing to check for patient antibodies against T. pallidum and direct detection techniques like animal inoculation and dark-field microscopy.

Serologic methods are further divided into two classes. Nontreponemal assays are one class of tests that look for antibodies to lipoidal antigens that are found in T. pallidum or the host. The results of these tests typically show reactivity, which may not be unique to syphilis but rather suggests host tissue damage. In addition to being widely used for screening, these tests are affordable, simple and indicative of syphilis when the appropriate clinical symptoms are present. Treponemal assays, which make up the other test class, employ particular treponemal antigens. Reactive treponemal testing is necessary to confirm the infection.  Compared to the nontreponemal tests, these tests are more costly and difficult to conduct.

Nonetheless, the recent diagnostic panels provide a variety of PCR, enzyme-linked immunosorbent assay, and direct antigen methods. Many of these methods have proven excellent in diagnosing congenital syphilis and neurosyphilis, which are challenging conditions to diagnose.

In summary, syphilis is diagnosed based on clinical findings, lesion material examination and serologic syphilis testing. Owing to its diverse manifestations which may occur in other infections, the disease often makes clinicians confused. A simple guide to choosing the appropriate test can aid in prompt diagnosis and save many lives.

References

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