Serum albumin and alkaline phosphatase levels as markers of neurosyphilis in syphilis patients

Objectives Existing evidence has linked albumin (ALB) and alkaline phosphatase (ALP) to various infectious or inflammatory conditions, but their association with neurosyphilis remains unreported. We aimed to investigate the associations between these liver function markers and disease activities and neurosyphilis in patients with syphilis. Methods This study included 448 HIV-negative syphilis patients with available data of serum ALB and ALP. Logistic regression models and restricted cubic splines were performed to investigate the associations of ALB, ALP, and ALB-to-ALP ratio (AAPR) with neurosyphilis. Results Serum ALB and ALP were correlated with blood WBC, serum TRUST titer and erythrocyte sedimentation rate. Liver function markers were associated with neurosyphilis, and the adjusted odds ratios (95% CIs) for the highest versus lowest tertiles of ALB, ALP and AAPR were 0.46 (0.22–0.95), 1.79 (1.05–3.04) and 0.53 (0.26–1.09), respectively. Multivariable-adjusted restricted cubic spline analyses suggested that there were dose-response relationships of ALB and ALP with neurosyphilis ( P for linearity < 0.05). The addition of ALB or ALP to the basic model with conventional risk factors improved risk reclassification for neurosyphilis, with the net reclassification improvement of 35.2 or 39.1%, and the integrated discrimination improvement of 1.8 or 1.1%, respectively (all P < 0.05). Conclusions Liver function markers, including ALB and ALP, were correlated with disease activity of syphilis and the likelihood of neurosyphilis in HIV-negative patients with syphilis. The findings suggested that these readily available routine indicators could serve as auxiliary tools for the monitoring and management of neurosyphilis.