Neurosyphilis might be difficult to diagnose particularly in asymptomatic patients and patients with HIV-coinfection. The objective of this study was to evaluate current diagnostic standards for neurosyphilis in HIV-positive and -negative patients.

We studied retrospectively patients with an active syphilis infection who had additionally undergone lumbar puncture. Patients where the criteria for the diagnosis of a definite or probable neurosyphilis were applicable were further analyzed for clinical symptoms, CSF, HIV-status as well as Treponema pallidum testing in serum and CSF. Correlation analysis of categorical variables was done by using the Chi-square test or in cases of small sample sizes the exact test of Fisher. p values ≤0.05 were considered significant.

Eighty-nine patients were diagnosed with syphilis. All necessary criteria for the diagnosis of a neurosyphilis were available in 67 of them including 35 HIV-positive and 32 HIV-negative patients. A definite neurosyphilis could be retrospectively diagnosed in 13 and a probable in another 25 cases. Normal CSF results were more likely in HIV-negatives (p = 0.016). A neurosyphilis was correlated to a CSF pleocytosis > 5 cells/µl and to an albumin quotient >7.8 mg/dl regardless of a parallel HIV infection. HIV-positives had more frequently a CSF-RPR titre >1:4 than HIV-negatives (p = 0.031). However, the RPR test in CSF in definite or probable neurosyphilis had a sensitivity of only 21 %.

Our data show that a pleocytosis and an elevated albumin quotient correlate with neurosyphilis. However, the CSF-RPR test as gold standard in neurosyphilis diagnostics has a very low sensitivity.

Table 2

Predictive parameters for definite or probable neurosyphilis

Parameter	Odds ratio	p value*
Serum-RPR-titre ≥32	1.53	0.383
CD4+ cell count ≤350/µl	1.1	0.612
Blood-CSF barrier disturbance in HIV-negatives	9	0.018**
Blood-CSF barrier disturbance in HIV-positives	6	0.027**
Albumin quotient >7.8 mg/dl in HIV-negatives	8.0	0.026**
Albumin quotient >7.8 mg/dl in HIV-positives	23.3	0.006**
Pleocytosis >5 cells/µl in HIV-negatives	6.7	0.006**
Pleocytosis >5 cells/µl in HIV-positives	8.3	0.015**
ITPA index >2 in HIV-negatives	7.6	0.025**
positive IgM-FTA-ABS test in HIV-negatives	13.1	0.022**