Clinical significance of cerebrospinal fluid tests for neurosyphilis

Abstract

From 1978 to 1987, 1,665 cerebrospinal fluid (CSF) fluorescent treponemal antibody absorption (CSF-FTA-ABS) tests were performed as the screening procedure for neurosyphilis. The CSF samples from 48 patients were reactive, and the medical history and results of the CSF–Venereal Disease Research Laboratory test (CSF-VDRL) for syphilis for 38 of these patients were reviewed. Likely active neurosyphilis was diagnosed if the patient had a reactive CSF-FTA-ABS test, recent onset of neurological signs consistent with neurosyphilis, abnormal CSF, and no other recognized cause for the neurological illness. Fifteen patients were so classified. Four had a reactive CSF-VDRL test. The specificity of the CSF-VDRL in diagnosing likely active neurosyphilis was 100%, but the sensitivity was only 27%. The insensitivity of the CSF-VDRL test limits its usefulness as a screening test for neurosyphilis. The CSF-FTA-ABS test appears more sensitive for screening but is less specific than the CSF-VDRL test in distinguishing currently active neurosyphilis from past syphilis. These findings imply that clinical judgment is still essential in establishing the diagnosis of active neurosyphilis.