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Syphilis Serology: Nontreponemal Tests

  • Test positive if lipoidal antigen from damaged host tissues or treponemes are present in plasma or serum
  • Reagent contains cardiolipin, lecithin and cholesterol
  • Tests for IgM and IgG antibodies
  • Rapid plasma reagin (RPR) is the most convenient test because the antigen is prepared
  • Venereal disease research laboratory (VDRL) test must be used when testing spinal fluid; RPR cannot be performed on cerebral spinal fluid
  • RPR and VDRL are 78-86% positive in primary syphilis
  • In secondary syphilis both tests are 100% positive
  • 95-98% of patients will be positive in latent syphilis
  • 1-2% of tests will be biological false positive reactions
  • Eventually nontreponemal test become negative with successful treatment, especially if the patient is treated in primary syphilis