Background: The cerebrospinal fluid (CSF)-Venereal Disease Research Laboratory (VDRL) test is only 27% sensitive for diagnosing neurosyphilis. Discriminant analysis, used on 124 patients, shows that other commonly used laboratory tests can, in combination, identify 87% of patients with neurosyphilis with 94% specificity.
Study design: The insensitivity of the CSF-VDRL (27% in persons with neurosyphilis) and the foreseen greater need to identify and treat neurosyphilis in the era of human immunodeficiency virus caused us to analyze the serum and cerebrospinal fluid results of 73 patients with syphilis and of 51 patients with clinically diagnosed neurosyphilis. Discriminant analysis was applied to different sets of laboratory tests to find the combination of test results best able to predict retrospectively the clinical diagnosis of syphilis or neurosyphilis, without reference to the CSF-VDRL.
Results: The predicting function averages 94% specificity and 87% sensitivity. Test result variables considered together are: CSF-FTA-ABS, serum FTA-ABS, CSF-TPHA, serum TPHA, and CSF cells.
Conclusions: The authors conclude that clinicians or laboratories can, independently of the CSF-VDRL, compute a score showing whether the results of a set of commonly used tests suggest neurosyphilis in a patient.