Treponemal Specific Test

Aka: Treponemal Specific Test, Treponemal Test, Treponema Pallidum Antibody Confirmatory Test, Rapid Treponemal Immunoassay, Manual Treponemal Assay, Treponemal Enzyme Immunoassay, Syphilis EIA, Treponemal Chemiluminescence Immunoassay, Syphilis CIA, Microbead Immunoassay, Syphilis MBIA, Fluorescent Treponemal Antibody, FTA, FTA-ABS, Treponema Pallidum Particle Agglutination Assay, TP-PA, Microhemagglutination Treponema Pallidum, MHA-TP

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II. Indications: Syphilis Testing

  1. Rapid Treponemal Immunoassays
    1. Reverse sequence Syphilis Screening (first step)
    2. Confirmed with a Non-Treponemal Test such as RPR or VDRL (and the manual TP-PA if needed for discrepancy)
  2. Manual Treponemal Assays
    1. Confirmation of positive Non-Treponemal Test in standard sequence testing OR
    2. Confirmation in reverse sequence testing with positive rapid immunoassay, but negative RPR/VDRL

III. Mechanism

  1. Treponemal Antigen precipitates Antibody
  2. Treponemal Test (using specific Treponemal Antigen)
    1. Contrast with Non-Treponemal Tests (e.g. RPR or VDRL) using cardiolipin/lecithin extract from beef heart
  3. Confirm positive with MHA-TP (See Syphilis Serology)

IV. Labs: Rapid Treponemal Immunoassays

  1. Indications
    1. Rapid Immunoassays are used as a first step in reverse sequence Syphilis Screening (see Syphilis Testing)
    2. Automated processing and high Test Sensitivity allows for cost effective sample processing
      1. Confirmed with a Non-Treponemal Test such as RPR or VDRL (reverse sequence)
      2. Discrepant tests (positive immunoassay, negative RPR/VDRL) is confirmed with Manual Assay (e.g. TP-PA)
  2. Methadologies (dozens of available immunoassays)
    1. Enzyme immunoassay (EIA)
    2. Chemiluminescence immunoassays (CIA)
    3. Microbead Immunoassays (MBIA)
  3. Composite Immunoassay efficacy
    1. Test Specificity >94% (except 83% for TrepSure)
    2. Test Sensitivity: 94 to 100%
      1. Primary Syphilis: >94% (most assays)
      2. Secondary Syphilis: 100%
      3. Early Latent Syphilis: 95% to 100%
      4. Late Latent Syphilis: 92% to 100%

V. Labs: Manual Treponemal Assays

  1. Background
    1. High Test Specificity and sensitivity allows for definitive confirmatory testing (esp. TP-PA)
  2. Indications
    1. Confirmation of positive Non-Treponemal Test in standard sequence testing OR
    2. Confirmation in reverse sequence testing with positive rapid immunoassay, but negative RPR/VDRL
  3. Treponema Pallidum Particle Agglutination Assay (TP-PA)
    1. Highest efficacy of the Manual Treponemal Assays
    2. Test Specificity: 99%
    3. Test Sensitivity
      1. Primary Syphilis: 86 to 100%
      2. Secondary Syphilis: 100%
      3. Early Latent Syphilis: 94 to 100%
      4. Late Latent Syphilis: 87 to 100%
  4. Fluorescent Treponemal Antibody (FTA-ABS)
    1. Test Specificity: 87-100%
    2. Test Sensitivity
      1. Primary Syphilis: 78 to 100%
      2. Secondary Syphilis: 93 to 100%
      3. Early Latent Syphilis: 94 to 100%
      4. Late Latent Syphilis: 84 to 93%
  5. Microhemagglutination - Treponema pallidum (MHA-TP)
    1. Test Specificity: 99%
    2. Test Sensitivity
      1. Primary Syphilis: 46 to 89%
      2. Secondary Syphilis: 90 to 100%
      3. Early Latent Syphilis: 94 to 100%
      4. Late Latent Syphilis: 97%

VI. Causes: Negative Test (Non-reactive)

  1. Syphilis absent
  2. False Negatives
    1. Early Primary Syphilis (first 2 weeks after infection)
    2. Late Latent Syphilis

VII. Causes: Positive Test (Reactive)

  1. Syphilis
  2. Other Treponemal disease (no current test as of 2025 differentiates between other Treponemal species)
    1. Yaws
    2. Pinta
    3. Bejel

VIII. References

  1. Park (2020) Clin Infect Dis 71(Suppl 1):S13-20 +PMID: 32578866 [PubMed]

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