Virology / Serology - Syphilis
Syphilis, a disease caused by infection with the bacterium Treponema pallidum, can be readily diagnosed by serologic methods. Serologic assays used to screen patients for syphilis are nontreponemal tests. The nontreponemal test performed in this laboratory is the Toludine Red Unheated Serum Test (TRUST). Confirmation of reactive screening test results (TRUST) is obtained through the use of specific treponemal tests for syphilis. The CAPTIA Syphilis-G (Treponema pallidum) EIA is performed in this laboratory to confirm syphilis screening test results when appropriate.
Specimen Acceptance Policy
The nontreponemal test for syphilis (TRUST) performed on serum is available only to local health departments and state-operated health facilities. The specific treponemal test for syphilis (CAPTIA Syphilis-G EIA) is available to all health care providers but is not designed to be a screening procedure and thus is only performed when required for proper patient management.
Submitted specimens must be accompanied by a fully completed DHHS #3445 or DHHS #3446. Failure to supply the requested patient information may result in significantly delayed specimen testing or compromised test results. Only serum may be submitted for primary serologic syphilis testing. Specimens submitted for diagnostic testing not labeled with correct patient identification information will not be tested. Minimal patient specimen identification includes full first and last name and either SSN or date of birth. Specimens which, for any reason, are deemed unsuitable or inappropriate for diagnostic testing will not be tested and will be discarded. Specimens received without a test requisition will be properly stored for ten days pending verbal and/or written notification of the submitter. Unless a test requisition is received, the specimen will be discarded at the end of the holding period.
All screening tests performed in this laboratory which are determined to be reactive will be confirmed by the CAPTIA Syphilis-G EIA, unless a previous positive confirmatory test result (CAPTIA Syphilis-G EIA, TP-PA, or FTA-ABS) is on file at the laboratory. In those cases, only the screening test results will be reported.
A request to this laboratory for a CAPTIA Syphilis-G EIA test must be accompanied by a quantitative screening test result, i.e., the submitter must provide a titer. This request will yield only a qualitative CAPTIA Syphilis-G EIA result without performing a screening test. If a previous positive confirmatory test result (CAPTIA Syphilis-G EIA, TP-PA, or FTA-ABS) is on file at the laboratory, no testing will be performed.
For the purposes of evaluating patients suspected of having late syphilis, the CAPTIA Syphilis-G EIA will be performed in this laboratory on serum regardless of the screening test result. Under these circumstances, the submitter must specifically request a CAPTIA Syphilis-G EIA, state the quantitative screening test result/titer, and indicate that late syphilis is suspected.
Specimen Collection
To collect ≥ 2 mL of serum, draw ≥ 5 mL of blood into a red top vacuum tube, serum separator tube, or equivalent and let stand for ≥ 30 minutes to ensure complete clotting of the blood. Centrifuge the sample for 5-10 minutes at ≥ 1,000 x G. Transfer serum to a plastic screw-capped vial. Clearly label each vial of serum with the patient’s full first and last name and either SSN or date of birth. Grossly hemolyzed, icteric, or lipemic serum is unacceptable for syphilis serologic assays. For TRUST screening, complete DHHS Form #3446; for the CAPTIA Syphilis-G EIA test, complete DHHS Form #3445.
Specimen Shipping
Properly identified vials of patient sera along with the completed submission forms should be sent in white colored specimen mailers labeled SYPHILIS SEROLOGY. For detailed shipping instructions using the double mailers, see Packing Instructions Using Outer Baggie. Ship at ambient temperature by the State Courier or U.S. Mail.
Serum transport tubes, DHHS #3446 for TRUST screening, and white colored specimen mailers are available through the NCSLPH online supply ordering system at this website. DHHS #3445 for CAPTIA Syphilis-G EIA tests may be downloaded and printed from this website.
Specimen Reporting
Results of nontreponemal tests for syphilis (TRUST) performed on serum are available within one working day after receipt of the specimen. Treponemal specific tests (CAPTIA Syphilis-G EIA) performed on serum are available within two working days after receipt of the specimen.
Patients with primary syphilis may have a nonreactive TRUST and/or CAPTIA Syphilis-G EIA when first seen; however, these tests will usually become reactive soon thereafter. Most patients treated for primary syphilis have a reversion of nontreponemal tests to nonreactive within 2-3 years. The CAPTIA Syphilis-G EIA will remain reactive after treatment. Nonreactive serologic tests and normal clinical evaluations do not exclude incubating syphilis.
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See also:
- About Virology / Serology
- Chlamydia
- HIV
- Hepatitis
- Syphilis
- Special Serology
- CDC Referral
- Arbovirus
- Norovirus
