Alternative cerebrospinal fluid tests to diagnose neurosyphilis in HIV-infected individuals

Abstract

Neurosyphilis is commonly present in patients with ocular syphilis who are also infected by HIV. The diagnosis of neurosyphilis may be difficult as up to 70% of HIV-positive patients with neurosyphilis have a negative cerebrospinal fluid (CSF)-Venereal Disease Research Laboratory (VDRL) test. The aim of this study was to identify alternatives to the CSF-VDRL test for the diagnosis of neurosyphilis in HIV-infected individuals. CSF fluorescent treponemal antibody (FTA) reactivity and % CSF lymphocytes that were B cells in fresh and frozen samples were determined for 47 HIV-infected cases with syphilis and 26 HIV-infected controls. As for serum, CSF fluorescent treponemal antibody reactivity ≥2+ was considered positive. Based on the results in controls and cases with normal CSF measures, cut-offs for elevated CSF B cells were proposed to be ≥9% in fresh and ≥20% in frozen samples. Neurosyphilis was defined as a reactive CSF-VDRL. The authors found that CSF-FTA-ABS (absorbed) and CSF-FTA (unabsorbed and undiluted) were 100% sensitive for the diagnosis of neurosyphilis. Elevated % CSF B cells in fresh and cryopreserved samples was specific (100%) but not sensitive (40 and 43%) in post hoc analyses. The results of CSF-FTA and assessment of % CSF B cells together allowed 16% of cases with pleocytosis but nonreactive CSF-VDRL to be diagnosed with neurosyphilis and 26% to be diagnosed as not having neurosyphilis. The authors conclude that when the CSF-VDRL is nonreactive, CSF-FTA and % CSF B cells may help exclude or establish the diagnosis of neurosyphilis.—Valerie Biousse