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NC Department of Health and Human Services
State Laboratory of Public Health
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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 RPR. Confirmation of reactive screening test results (RPR) is obtained through the use of specific treponemal tests for syphilis. The SYPHILIS TP CMIA, which detects both IgM and IgG antibodies to T. pallidum, is performed in this laboratory to confirm syphilis screening test results when appropriate.

Specimen Acceptance Policy

The nontreponemal test for syphilis (RPR) performed on serum is available only to local health departments and state-operated health facilities. The specific treponemal test for syphilis (SYPHILIS TP CMIA) 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 Syphilis Serology Form #3446 (PDF, 96 KB). 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, date of birth, or other unique identifier. 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 SYPHILIS TP CMIA, unless a previous positive SYPHILIS TP CMIA or other confirmatory test result is on file at the laboratory. In those cases, only the screening test results will be reported.

A request to this laboratory for a SYPHILIS TP CMIA 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 SYPHILIS TP CMIA result without performing a screening test. If a previous positive SYPHILIS TP CMIA or other confirmatory test result is on file at the laboratory, no testing will be performed.

For the purposes of evaluating patients suspected of having late syphilis, the SYPHILIS TP CMIA will be performed in this laboratory on serum regardless of the screening test result. Under these circumstances, the submitter must specifically request a SYPHILIS TP CMIA, 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, date of birth, or other unique identifier. Grossly hemolyzed, icteric, or lipemic serum is unacceptable for syphilis serologic assays. Complete DHHS Syphilis Serology Form #3446 (PDF, 96 KB).

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 (PDF, 4.6 MB). Ship at ambient temperature by the State Courier or U.S. Mail.

Serum transport tubes and white colored specimen mailers are available through the NCSLPH online supply ordering system at this website. The DHHS Syphilis Serology Form #3446 (PDF, 96 KB) may be downloaded and printed from this website.

Result Reporting

Results of nontreponemal tests for syphilis (RPR) performed on serum are available within three working days after receipt of the specimen. Treponemal specific tests (SYPHILIS TP CMIA) performed on serum are available within four working days after receipt of the specimen. These results can be accessed on Lab Test Results Lookup.

Patients with primary syphilis may have a nonreactive RPR and/or SYPHILIS TP CMIA 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 SYPHILIS TP CMIA will usually remain reactive after treatment. Nonreactive serologic tests and normal clinical evaluations do not exclude incubating syphilis.

Relevant Links

Virology/Serology Information