The Clinical Value Of Serological Activity Of Syphilis In Diagnosis And Prognosis Of Neurosyphilis

Background Diagnosis of neurosyphilis and its efficacy of treatment were based on cerebrospinal fluid(CSF) assessment through lumbar puncture. Previous researches on predictors of neurosyphilis mainly focus on human immunodeficiency virus(HIV)-infected syphilis patients. But these known predictors may be inapplicable to the HIV-negative populations since they have different characteristics. This study aimed to seek serological predictors for neurosyphilis among HIV-negative syphilis patients, and to determine whether decrease of non-treponemal and treponemal antibodies could predict normalization of CSF abnormalities.Methods From June 2005 to December 2014, a total of 414 HIV-negative syphilis patients were recruited, consisting of 197 neurosyphilis(including 129 confirmed neurosyphilis and68 probable neurosyphilis) and 217 syphilis/non-neurosyphilis. Clinical and laboratory characteristics of neurosyphilis were compared to syphilis/non-neurosyphilis to identify factors predictive of neurosyphilis. Serum rapid plasma reagin(RPR), Treponema pallidum particle agglutination(TPPA), and their parallel testing format for screening neurosyphilis were evaluated. Correlation between CSF abnormalities and serum RPR,serum TPPA titers were evaluated before and after treatment of neurosyphilis.Results The odds of neurosyphilis was positively associated with the serum RPR and TPPA titers. The serum TPPA titers had better performance than serum RPR titers in screening neurosyphilis. Serum RPR titer ≥1:4 and serum TPPA titer ≥1:2560 were the best cutoff points to identify neurosyphilis respectively. A parallel testing format of serum RPR titer ≥1:4 and serum TPPA titer ≥1:2560 could screen out 88.1% of neurosyphilis and97.6% of confirmed neurosyphilis. Serum RPR titer ≥1:4, serum TPPA titer ≥1:2560,male sex, elevated serum creatine kinase, history of psychiatric disorders, cerebral infarction and diabetes mellitus were associated with neurosyphilis. Serum RPR and TPPA titers were respectively correlated to CSF RPR and TPPA titers, CSF leukocytes and protein before treatment of neurosyphilis. After treatment, normalization of serum RPR, i.e. serological response, did good in predicting normalization of CSF abnormalities.Conclusions Quantitation of serum TPPA test is worthwhile and it even has better performance than serum RPR in screening neurosyphilis. Serum RPR and serum TPPA characteristics,male sex, serum creatine kinase, history of psychiatric disorders, cerebral infarction and diabetes mellitus can be predictors for neurosyphilis. Moreover, patients with both serum RPR titer <1:4 and serum TPPA titer <1:2560 have low probability of confirmed neurosyphilis, suggesting that it is reasonable to reduce lumbar puncture in such individuals. Meanwhile, in most instances, normalization of serum RPR titers could predict normalization of CSF abnormalities after treatment of neurosyphilis. Thus serum RPR titers can be used to evaluate the efficacy of treatment to avoid repeated lumbar puncture.