Syphilis IgG EIA

  • Laboratory Location – Central Laboratory
  • CPT Code – 86780
  • Synonyms – TP-PA, Syphilis, Treponema pallidum particle agglutination, Treponema pallidum
  • Test Description - Serodia® TP-PA is a qualitative gelatin article agglutination assay intended to be used for the detection of Treponema pallidum antibodies in human serum as an aid in the diagnosis of syphilis. The TP-PA is a reflex test that is perform when the Syphilis EIA is initially reactive and the VDRL is non-reactive. 

Possible Results

  • Non-Reactive
  • Inconclusive
  • Reactive

Reference Range

  • Non-Reactive

Specimen Requirements

  • Specimen Type - Serum
  • Specimen Container(s) - red top tubes, Marble top tubes, polypropylene vials
  • Minumum accepted volume - 1 mL

Specimen Collection Instructions

Blood should be collected in a plastic, sterile STD Program approved collection tube. Please follow the manufacturer's instructions on clot time and centrifuge speed/time requirements.

The Syphilis Serology Lab 16 form must be filled out completely. The following information must be included on the form:

  • Patient's Name
  • Patient's Date of Birth
  • Patient's Gender
  • Patient's race/ethnicity
  • Date and time of specimen collection
  • Test requested
  • Type of specimen collected
  • Submitter's name and address

Storage and Transport Instructions

Speciments should be shipped refrigerated (2-8ºC). Specimens can be stored for up to 5 days at 2-8ºC. For longer storage, specimens must be frozen at -20ºC or colder. Frozen specimens must be shipped on dry ice and received at a temperature of -20ºC or colder. Sera may be frozen and thawed only once.

Causes for Rejection

  • Improper labeling
  • expired collection tubes
  • unspun samples
  • tubes that contain less than 90% of the total drawing capacity (QNS)
  • Specimen age greater than 5 days if specimen has not been frozen at -20ºC or colder
  • Improper storage or improper transport temperature requirements are also reasons for rejection

Limitations for the Procedure

The Serodia® TP-PA test is specific for detecting Treponema pallidum antibodies in serum. It does not detect T. pallidum directly. As will all serological tests for syphilis, interpretation of results obtained with this test must be used in conjunction with the patient's clinical sypmtoms, medical history and other clinical and/or laboratory findings to produce an overall clinical diagnosis. All treponemal tests tend to remain reactive following treponemal infection; therefore, they should not be used to evaluate response to therapy. This test may be reactive in a small percentage (less than 1%) of normal or healthy persons; these false-positive results are often transient, their cause unknown. False positive results may occur in association with other underlying illnesses and may be reactive in persons from areas where yaws or pinta was, or is, endemic. Samples from patients with HIV, Leprosy, Toxoplasmosis, H. pylori, or drug addiction may react, on occasion, with either the sensitized or the unsensitized particles, causing false-positive or Inconclusive results. 

Interfering Substances

  • Specimens containing erythrocytes or other visible matter should be centrifuged prior to testing to prevent interference with test results.


  • Serodia® - TP-PA Package Insert
  • CaptiaTM Syphilis IgG EIA package insert
  • BD VDRL Antigen Package Insert


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