Syphilis laboratory tests


 * Darkfield examinations and tests to detect T. pallidum in lesion exudate or tissue are the definitive methods for diagnosing early syphilis.


 * Although no T. pallidum detection tests are commercially available, some laboratories provide locally developed PCR tests for the detection of T. pallidum.


 * A presumptive diagnosis of syphilis is possible with the use of two types of serologic tests:
 * nontreponemal tests (e.g., venereal disease research laboratory (VDRL) and rapid plasma reagent test) and
 * treponemal tests (e.g., fluorescent treponemal antibody absorbed (FTA-ABS) tests, the T. pallidum passive particle agglutination (TP-PA) assay, various enzyme immunoassays, and chemiluminescence immunoassays).


 * The use of only one type of serologic test is insufficient for diagnosis, because each type of test has limitations, including the possibility of false-positive test results in persons without syphilis.


 * False-positive nontreponemal test results can be associated with various medical conditions unrelated to syphilis, including autoimmune conditions, older age, and injection-drug use; therefore, persons with a reactive nontreponemal test should receive a treponemal test to confirm the diagnosis of syphilis.

Resources

 * Sexually transmitted diseases treatment guidelines, 2010


 * Association of Public Health Laboratories (APHL). Laboratory Diagnostic Testing for Treponema pallidum. Expert Consultation Meeting Summary Report, January 13--15, 2009, Atlanta, GA


 * CDC: Guidelines for the laboratory diagnosis of gonorrhea, chlamydia and syphilis