Bottom line: CSF VDRL is routinely ordered for diagnosis of neurosyphilis and is highly specific yet less sensitive. If clinical suspicion remains elevated in a negative CSF VDRL, testing with CSF FTA-ABS should be considered as the sensitivity is nearly 100% with a high negative predictive value for ruling out neurosyphilis.
Summary: DynaMed references the CDC guidelines for diagnosing neurosyphilis, which reports that VDRL is very specific, but sensitivity has been reported 20-70%. VDRL is used as a reference standard for neurosyphilis in many diagnosis cohort studies.
Dumaresq J, et al. Clinical prediction and diagnosis of neurosyphilis in HIV-infected patients with early syphilis. J Clin Microbiology. 2013; 51(12): 4060-4066. Retrospective study of 122 patients with documented HIV infection and early syphilis who were tested for neurosyphilis. The reference standard was a positive CSF VDRL test and/or white blood cell count >20 cells/µl. Sensitivity of CSF FTA-ABS was 100% and specificity was 12%. Negative predictive value was 100%.
Harding AS, et al. The performance of cerebrospinal fluid treponemal-specific antibody tests in neorsyphilis: a systematic review. Sex Transm Dis. 2012 Apr; 39(4): 291-7.
The authors identified 3 studies that evaluated CSF FTA-ABS and used CSF VDRL as the reference standard. The three studies had patient populations (includes HIV positive and negative) of 597 (16% of patients had NS), 27 (42% of patients had NS), and 54 (13% of patients had NS and another 39% had syphilis but not NS). Sensitivity of CSF FTA-ABS was 100% in all three studies and specificity was 68-100%. Negative predictive value was 100%.