Neurosyphilis (NS) is a chronic infectious disease associated with Treponema pallidum subsp. pallidum (TP) infection of the central nervous system. The purpose of this study was to offer evidence for the diagnosis and treatment of NS by revealing the detection of TP DNA and CXCL13 concentration in the cerebrospinal fluid (CSF) of HIV-negative syphilis patients. Patients and Methods: This study included 75 syphilis patients. The frequency of TP invasion into the CSF was detected by nested PCR. ELISA was performed to detect CSF CXCL13 concentrations, and ROC analysis was performed to assess diagnostic accuracy. Sociodemographic data, clinical symptoms, and laboratory indices of patients were collected. CSF CXCL13 levels and clinical characteristics of syphilis patients were investigated retrospectively. Results: The detection rate of CSF DNA of TP by nested PCR was 5.3% and 16.7% in HIV-negative syphilis patients and NS patients, respectively. There was a significant difference between the NS and non-NS groups in terms of neurological symptoms, CSF TPPA, CSF TRUST, CSF nucleated cells, CSF protein, and CSF CXCL13 levels (P<0.05). ROC curve analysis showed that the AUC for CSF CXCL13 levels was 0.906 (95% CI 0.832-0.981, P <0.0001), with an optimal critical value of 57.85 pg/mL and sensitivity and specificity of 88.89% and 78.95%, respectively. Conclusion: Nested PCR can be used as an auxiliary diagnosis of NS, and CSF CXCL13 >60 pg/mL has high sensitivity and specificity for NS patients and non-NS patients. CXCL13 may be a useful marker to distinguish NS from non-NS syphilis in HIVnegative patients.

Objective To establish the risk scoring model for HIV-negative neurosyphilis (NS) patients and to optimize the lumbar puncture strategy. Methods From 2016 to 2021, clinical information on 319 syphilis patients was gathered. Multivariate logistic regression was used to examine the independent risk factors in NS patients who tested negative for human immunodeficiency virus (HIV). Receiver operating characteristic curves (ROC) were used to assess the risk scoring model’s capacity for identification. According to scoring model, the timing of lumbar puncture was suggested. Results There were statistically significant differences between HIV-negative NS and non-neurosyphilis (NNS) patients in the following factors. These included age, gender, neuropsychiatric symptoms (including visual abnormalities, hearing abnormalities, memory abnormalities, mental abnormalities, paresthesia, seizures, headache, dizziness), serum toluidine red unheated serum test (TRUST), cerebrospinal fluid Treponema pallidum particle agglutination test (CSF-TPPA), cerebrospinal fluid white blood cell count (CSF-WBC), and cerebrospinal fluid protein quantification (CSF-Pro) (P < 0.05). Logistic regression analysis of HIV-negative NS patients risk factors showed that age, gender, and serum TRUST were independent risk factors for HIV-negative NS (P = 0.000). The total risk score (− 1 ~ 11 points) was obtained by adding the weight scores of each risk factor. And the predicted probability of NS in HIV-negative syphilis patients (1.6 ~ 86.6%) was calculated under the corresponding rating. ROC calculation results showed that the score had good discrimination value for HIV-negative NS and NNS: area under the curve (AUC) was 0.80, the standard error was 0.026 and 95% CI was 74.9–85.1% (P = 0.000). Conclusion The risk scoring model in this study can classify the risk of neurosyphilis in syphilis patients, optimize the lumbar puncture strategy to a certain extent, and provide ideas for the clinical diagnosis and treatment of HIV-negative neurosyphilis.

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