Syphilis is a sexually transmitted infection caused by the spirochete Treponema pallidum. OnSite HIV/Syphilis Ab Combo Rapid Test has been a major infection in man throughout recorded history and has challenged physicians with its many clinical manifestations. The rate of primary and secondary syphilis in the United States increased steadily from 2001 to 2009 with a slight decline in 2010. During this period, the proportion of infections observed in men who have sex with men (MSM) has increased. This infection can also be associated with the transmission or presence of other sexually transmitted diseases.
The total number of syphilis cases in the United States in 2011 reached 46,042, a slight increase of 0.4% over the previous year. Diagnosis is based primarily on clinical findings and serologic testing, as the organism is not found. can be cultivated in vitro. The clinical manifestations of the disease are classified by stages: primary, secondary, latent, and late or tertiary syphilis, including neurosyphilis and cardiovascular syphilis. Confirmation of the diagnosis is made by serological tests. Since no single test is capable of diagnosing active syphilis, a combination of treponemal and nontreponemal tests is used.
Clinical manifestations of syphilis.
After acquiring the infection, the asymptomatic incubation phase lasts an average of 21 days (3 to 90 days). The patient may then develop a variety of clinical findings, which have classically been divided into clinical stages.
- Primary syphilis
This stage is characterized by a painless genital, anal, or, less commonly, oral ulcer or chancre. This lesion occurs at the inoculation site. The ulcer is usually indurated and usually without exudate. There may be regional lymphadenopathy.
- Secondary syphilis
This stage usually develops weeks to a few months after acquisition in a portion of untreated patients. The most common manifestation is a diffuse maculopapular rash involving the trunk, extremities, palms, and soles. This is a systemic disease and the rash is often accompanied by fever, malaise, myalgias, sore throat, headaches and weight loss. Hepatitis, patchy alopecia and renal failure may also be seen. Ocular manifestations may include uveitis, retinitis, and optic neuritis. CNS invasion is also seen in the early stages of untreated disease and may be associated with aseptic meningitis, cranial neuropathies, or meningovascular manifestations.
- Latent syphilis
This stage is characterized by the absence of signs or symptoms of infection but is associated with positive serologic tests. Early latent syphilis has been defined as an infection of 1 year or less. Other asymptomatic states are classified as late latent syphilis or latent syphilis of unknown duration.
- Late (tertiary) syphilis
A progressive dementing illness (general paresis) and tabes dorsalis are considered the classic late neurologic manifestation of the disease. Aortitis and gummy syphilis (nodular lesions that occur most often on the skin and bones) are other clinical manifestations of this stage.
Diagnostic tests for syphilis
- Direct detection methods
Although these methods are not widely available, there are several tests that can be used to directly detect the organism. These include dark field microscopy, PCR, and direct fluorescent antibody tests for T pallidum. In some cases, these tests may allow diagnosis of syphilis prior to a serologic response. However, most clinical centres do not have access to these methods and must rely on clinical manifestations and serologic tests.
- Treponemal tests
Tests available in the United States include the T pallidum microhemagglutination assay, T pallidum particle agglutination, T pallidum hemagglutination assay, fluorescent treponemal antibody absorption test (FTA-ABS), and chemiluminescence immunoassays. and enzyme immunoassays that detect treponemal antibodies. The results of these tests are generally reported as either reactive or non-reactive. Reactivity to a treponemal test implies infection but does not determine whether the infection is recent or remote or whether it has been treated or not. False-positive results can occur with this type of test and may be due to other infections or other inflammatory conditions, such as systemic lupus erythematosus.
- Nontreponemal tests
There are three types of nontreponemal tests available in the United States: the rapid plasma reagin (RPR), the Venereal Disease Research Laboratory (VDRL) test, and the toluidine red unheated serum test. These tests generally react with immunoglobulin M and immunoglobulin G antibodies. The results of these tests are semiquantitative, reflect the activity of the infection, and are reported as an antibody titer that reflects the number of dilutions at which activity is still detected. Seroconversion occurs in about 3 weeks but can take up to 6 weeks. Consequently, patients may present with primary syphilis and have initially negative serologic tests. Titers will normally decrease over time, often to undetectable titers after successful treatment. False-positive nontreponemal tests have been reported in systemic infections such as tuberculosis, rickettsiosis, and endocarditis, and also during pregnancy.