What tests are positive for syphilis?

From the Guidelines

Syphilis testing typically involves two types of tests: nontreponemal and treponemal tests, with the most recent and highest quality study suggesting that a reverse algorithm, starting with a treponemal test and confirming positive results with a nontreponemal test, is commonly used in many labs 1.

Types of Tests

• Nontreponemal tests:
  • Rapid Plasma Reagin (RPR)
  • Venereal Disease Research Laboratory (VDRL)
• Treponemal tests:
  • Treponema pallidum Particle Agglutination (TP-PA)
  • Fluorescent Treponemal Antibody Absorption (FTA-ABS)
  • Enzyme Immunoassays (EIAs)
  • Chemiluminescence Immunoassays (CIAs)
  • Rapid point-of-care tests

Testing Algorithm

• Traditional algorithm: nontreponemal test followed by treponemal test if positive
• Reverse algorithm: treponemal test followed by nontreponemal test if positive

Direct Detection

• Darkfield microscopy: identifies spirochetes in lesion samples during primary or secondary syphilis
• PCR tests: detects Treponema pallidum DNA in various specimens

Diagnosis

• Proper diagnosis requires correlation of test results with clinical findings and patient history, as stated in the 2020 study 1.
• The 2018 study 1 also emphasizes the importance of using both nontreponemal and treponemal tests for accurate diagnosis.

From the Research

Syphilis Tests

The following tests can be positive for syphilis:

• Venereal Disease Research Laboratory (VDRL) test 2, 3, 4, 5
• Treponema pallidum particle agglutination (TP-PA) test 2, 6
• Rapid Plasma Reagin (RPR) test 2, 3, 4, 5
• Fluorescent treponemal antibody absorption (FTA-ABS) test 4
• Trep-Chek IgG Enzyme Immunoassay (Trep-Chek IgG EIA) 4
• Innogenetics INNO-LIA 4
• Abbot Determine 5
• Abbot Syfacard-RR (RPR card test) 5
• Biorapid Syphilis (one-step immunochromatographic test) 6
• Bioelisa Syphilis 3.0 (ELISA) 6
• ETI-Treponema Plus (ELISA) 6

Test Sensitivities

The sensitivities of these tests vary:

• VDRL test: 71% 2, 70.8% 3
• TP-PA test: 86% 2
• RPR test: 75% 3, 56.3% 5
• Trep-Chek IgG EIA: 85.3% 4
• Biorapid Syphilis: 92% 6
• Bioelisa Syphilis 3.0: 100% 6
• ETI-Treponema Plus: 100% 6
• Abbot Determine: 92.0% 5
• Abbot Syfacard-RR (RPR card test): 56.3% 5

Test Specificities

The specificities of these tests also vary:

• VDRL test: 99% 3
• RPR test: 99.3% 3, 96.5% 5
• Trep-Chek IgG EIA: 95.6% 4
• Biorapid Syphilis: 79% 6
• Bioelisa Syphilis 3.0: 100% 6
• ETI-Treponema Plus: 100% 6
• Abbot Determine: 94.6% 5
• Abbot Syfacard-RR (RPR card test): 96.5% 5