Is there a test for syphilis?

From the Guidelines

Yes, there are several tests for syphilis, and the most common approach involves using a combination of treponemal and non-treponemal tests, as recommended by the Infectious Diseases Society of America and the American Society for Microbiology in 2018 1. The tests for syphilis include:

• Treponemal tests, such as fluorescent treponemal antibody absorbed (FTA-ABS) and Treponema pallidum particle agglutination (TP-PA)
• Non-treponemal tests, such as Venereal Disease Research Laboratory (VDRL) and Rapid Plasma Reagin (RPR)
• Darkfield examinations and direct fluorescent antibody tests of lesion exudate or tissue for definitive diagnosis of early syphilis These tests detect antibodies produced by the body in response to the syphilis bacterium. For initial screening, healthcare providers typically use either a treponemal test followed by a non-treponemal test if positive (traditional approach) or vice versa (reverse sequence) 1. If symptoms of syphilis are present, a doctor might also take a sample from a sore for direct testing under a microscope (darkfield microscopy) or for PCR testing. Testing is crucial because syphilis can be easily treated with antibiotics (usually penicillin G) in its early stages, but can cause serious health problems if left untreated 1. The CDC recommends testing for anyone with symptoms, pregnant women, men who have sex with men, people with HIV, and those with sexual partners who have tested positive for syphilis. Most tests can detect syphilis within 1-3 weeks after infection, though it may take longer for some tests to become positive. It's essential to note that a patient who has a reactive treponemal test usually will have a reactive test for a lifetime, regardless of treatment or disease activity, and nontreponemal test antibody titers usually correlate with disease activity 1.

From the Research

Syphilis Testing

• Syphilis has several clinical manifestations, making laboratory testing a crucial aspect of diagnosis 2.
• Serological testing is the most frequently used approach in the laboratory diagnosis of syphilis, as the etiological agent, Treponema pallidum, cannot be cultured 2.
• Various serological and alternative tests are available, including:
  • Venereal Diseases Research Laboratory (VDRL) test
  • Treponema pallidum particle agglutination assay (TPPA)
  • Fluorescent treponemal antibody absorption (FTA-ABS) test
  • Enzyme immunoassay (EIA) tests, such as the Murex EIA and Mercia antitreponemal IgM EIA 3, 4
• Automated tests, such as the HiSens Auto Rapid Plasma Reagin (AutoRPR) and AutoTPPA, have been developed and compared to conventional methods, showing high concordance rates and potential as alternatives to conventional syphilis tests 3.
• The choice of test depends on the clinical stage of the disease and the patient's history, with some tests being more suitable for diagnosis and others for treatment monitoring 3, 4.

Test Characteristics

• The VDRL test has higher sensitivity than the AutoRPR test, but lower specificity 3.
• The FTA-ABS and AutoTPPA tests have high sensitivities and specificities, greater than 98.0% 3.
• The Mercia IgM EIA is useful for detecting early syphilis, particularly in patients with suspected syphilis or known contacts 4.
• Antibody titers in the VDRL and TPPA tests increase as the infection progresses 4.

Diagnostic Approaches

• Dark field microscopy can be used for diagnosis in early syphilis 5.
• Rapid "desktop" serological tests may simplify and promote widespread screening for syphilis 5.
• Laboratory methods, including direct detection of T. pallidum and detection of phospholipid and treponemal antibodies, are used for diagnosis 6.