Cerebrospinal fluid tau protein is increased in neurosyphilis: a discrimination from syphilis without nervous system involvement?

OBJECTIVE: The objective of this study was to investigate the levels of tau protein in neurosyphilis. STUDY DESIGN: Total tau protein in the cerebrospinal fluid of 12 patients with neurosyphilis, 17 with syphilis without nervous system involvement, 14 controls, and 14 patients with Alzheimer disease of comparable age were analyzed. Double-sandwich enzyme-linked immunosorbent assay was used for measurements. RESULTS: Increased levels of cerebrospinal fluid total tau were observed in neurosyphilis (median [25th-75th percentile]: 349 pg/mL [312-429]) and in Alzheimer disease (543 [441-1017]) as compared with the controls (189 [106-220]) and syphilis without nervous system involvement (190 [160-223]). Using a cutoff level of 300 pg/mL, increased tau discriminated cases of neurosyphilis from syphilis without nervous system involvement with a sensitivity and specificity of 83% and 94%, respectively. CONCLUSIONS: These results indicate that increased total tau may be useful in the discrimination of neurosyphilis from syphilis without nervous system involvement.