To investigate whether cerebrospinal fluid (CSF) toluidine red unheated serum test (TRUST) could replace venereal disease research laboratory test (VDRL) in laboratory diagnosis of neurosyphilis, and the difference in the auxiliary diagnostic effect of cerebrospinal fluid examination [including white blood cell (WBC) count and protein levels].

Total of 122 untreated patients with human immunodeficiency virus (HIV)-negative neurosyphilis who were first diagnosed in Beijing Ditan Hospital, Capital Medical University from April 2013 to July 2018 were enrolled. The patients were divided into asymptomatic group (60 cases), early neurosyphilis group (17 cases) and late neurosyphilis group (45 cases). The detection rate and consistency of CSF-VDRL and CSF-TRUST in each group were evaluated by Fisher exact probability test and Kappa test, and the retrospective analysis of WBC count and protein content in cerebrospinal fluid of VDRL positive patients were performed to evaluate the auxiliary diagnostic effect of routine CSF examination.

The positive rates of CSF-VDRL in asymptomatic group, early and late neurosyphilis groups were 46.7% (28/60), 100% (17/17) and 97.8% (44/45), respectively, and the positive rates of CSF-TRUST were 43.3% (26/60), 64.7% (11/17) and 86.7% (39/45), respectively. The positive rates of CSF-VDRL and CSF-TRUST were not significantly different in asymptomatic group (P = 0.804) and late neurosyphilis group (P = 0.063), however, there was significant difference in early neurosyphilis group (P = 0.031). Kappa coefficients of diagnosis results of CSF-VDRL and CSF-TRUST were 0.462 (P < 0.001) and 0.257 (P = 0.01) in asymptomatic group and late neurosyphilis group, respectively, indicating that consistency between the two detection methods was moderate. The sensitivity of CSF WBC count of patients with CSF-VDRL positive in asymptomatic group, early and late neurosyphilis groups were 71.4% (20/28), 70.6% (12/17) and 77.3% (34/44), respectively, and the sensitivity of CSF protein level were 35.7% (10/28), 70.6% (12/17) and 81.8% (36/44), respectively. The sensitivity of CSF WBC count and CSF protein of patients with VDRL positive in asymptomatic neurosyphilis group were significantly different (χ² = 7.179, P = 0.007). The sensitivity of CSF protein level of patients with VDRL positive and TRUST positive in the early neurosyphilis group were significantly different (χ² = 3.939, P = 0.047).

CSF-TRUST could replace CSF-VDRL in the diagnosis of asymptomatic and late neurosyphilis patients, however, the detection rate of CSF-TRUST of patients with early neurosyphilis was lower than that of CSF-VDRL. Because of the poor consistency of CSF-VDRL and CSF-TRUST, the detection rate of neurosyphilis could be greatly improved if the two methods were carried out at the same time.