non-treponemal tests (for syphilis)
Chapter: 9b
These serologic tests are most useful for screening. They are very sensitive, but specificity is a problem. Patients with rheumatoid arthritis, systemic lupus, and other diseases may react positively. Such results must be confirmed by the more specifec treponemal tests for syphilis, before you tell the patient that they have syphilis! These tests take advantage of antibodies to a tissue lipids called cardiolipin. These antibodies are produced as an after-effect of treponemal infection. The most common tests are the Rapid Plasma Reagin card (RPR), and the Venereal Disease Research Laboratory test (VDRL). Both tests are quite similar. You have an example of the RPR test in your Supplemental Image Database.