To investigate the clinical significance of oligoclonal bands (OB) in the diagnosis of neurosyphilis.

Total of 163 HIV-negative syphilis patients who first diagnosed and untreated were enrolled in Capital Medical University, Beijing Ditan Hospital from June 2018 to December 2018. The patients were divided into latent syphilis group (39 cases), asymptomatic neurosyphilis group (43 cases) and symptomatic neurosyphilis group (81 cases). Cerebrospinal fluid and serum OB were detected by isoelectric focusing combined with silver staining in all enrolled patients, and the positive result of cerebrospinal fluid OB was determined. The difference in OB positive rate between latent syphilis and neurosyphilis patients was compared. The biochemical and routine indexes differences of cerebrospinal fluid between OB positive and negative neurosyphilis patients were analyzed. The efficacy of OB in the diagnosis of neurosyphilis was evaluated by ROC curve.

Total of 163 patients were enrolled, among whom, 97 cases were detected for OB positive in cerebrospinal fluid. The positive rates of OB were 12.8% (5/39), 65.1% (28/43) and 79.0% (64/81) in latent syphilis group, asymptomatic neurosyphilis group and symptomatic neurosyphilis group, respectively. The positive rates of OB in cases of asymptomatic neurosyphilis group [28 (65.1%)] and symptomatic neurosyphilis group [64 (79.0%)] were significantly higher than that of latent syphilis group [5 (12.8%)], with significant difference (Bonferroni correction, P < 0.0167). The positive rates of OB in all subtypes of symptomatic neurosyphilis were 93.3% (14/15) for tabes dorsalis, 89.5% (34/38) for general paresis, 81.8% (9/11) for meningovascular neurosyphilis and 41.2% (7/17) for ocular syphilis. The OB positive rate of ocular syphilis was the lowest among symptomatic neurosyphilis subtypes, and was significantly different compared with general paresis and tabes dorsalis (Bonferroni correction, P < 0.008). The positive rate of OB in late neurosyphilis (90.6%, 48/53) was significantly higher than that of early neurosyphilis (68.5%, 37/54), with significant difference (χ² = 7.96, P = 0.005). The levels of IgG index and cerebrospinal fluid leukocyte, IgG, IgG synthesis rate, and total protein increased significantly in OB positive neurosyphilis patients compared with those of OB negative neurosyphilis patients. The specificity and sensitivity of OB positive in cerebrospinal fluid in the diagnosis of neurosyphilis were 87.2% and 74.2%, respectively. Compared with the "gold standard" for the diagnosis of neurosyphilis used in this study, the consistency rate was 78.6%. The area under the ROC curve was 0.81.

Compared with latent syphilis, the positive rate of OB in neurosyphilis increased significantly, suggesting that OB may have a certain diagnostic value for neurosyphilis. OB of cerebrospinal fluid could reflect the immunity of the central nervous system, and providing a certain objective basis for the application of cerebrospinal fluid OB in neurosyphilis.