The treponema-specific antibody tests by EIA (e.g. Trep-Sure) are much more sensitive and specific than RPR, especially during the primary and late stages of syphilis (1). A positive EIA treponema-specific test should be followed by an RPR to better assess disease activity. If the RPR is positive, further evaluation for neurosyphilis with lumbar puncture may be necessary. If the RPR is negative, a more specific treponema test (e.g. fluorescent tryponemal antibody [FTA], or Treponema pallidum particle agglutination[TP-PA]) should be performed for confirmation(1). Remember also that serum RPR may be negative in about 30% of patients with neurosyphilis (2); so a negative serum RPR does not rule out neurosyphilis.
1. Binnicker MJ, Jespersen DJ, Rollins LO. Treponema-specific tests for serodiagnosis of syphilis: comparative evaluation of seven assays 2011;49:1313-1317.
2. Whitefield SG, Everett As, Rein MF. Case 32-1991;tests for neurosyphilis. N Engl J Med 1992;326:1434..