Comparisons of several laboratory tests in the diagnosis of neurosyphilis

Abstract

Objective To compare the sensitivity and specificity of venereal disease research laboratory （VDRL） test versus several other laboratory tests in the diagnosis of neurosyphilis. Methods Lumber puncture was conducted to obtain cerebrospinal fluid （CSF） from untreated outpatients with latent syphilis （LS） or serofast outpatients with LS. Then, VDRL test, rapid plasma regain （RPR） test, Treponema pallidum particle agglutination （TPPA） assay, fluorescent treponemal antibody-absorption （FTA-ABS） test and protein quantification were performed on these CSF samples. The sensitivity, specificity, positive predictive value and negative predictive value were compared between VDRL test and four other laboratory tests in the diagnosis of neurosyphilis. Results Totally, 61 cases of latent syphilis were included in this study. The sensitivity, specificity,positive predictive value and negative predictive value were 93.44% （57/61）, 99.32%（293/295）, 96.61%（57/59）, 98.65% （293/297）for CSF-RPR, respectively, 91.80% （56/61）, 82.71% （244/295）, 52.34% （56/107）,97.99 （244/249） for CSF-TPPA, respectively, 93.44% （57/61）, 82.71% （244/295）, 52.78%（57/108）, 98.39%（244/248） for CSF-FTA-ABS, respectively, and 49.18%（30/61）, 97.29% （287/295）, 78.95% （30/38）,90.25% （287/318） for CSF protein quantification, respectively. Conclusions CSF-VDRL cannot be replaced by CSF-RPR, -TPPA, -FTA-ABS, or CSF protein quantification in the diagnosis of neurosyphilis. CSF-RPR shows a high sensitivity and specificity in the diagnosis of neurosyphilis, with an increased diagnostic capability （area under the receiver operating characteristic curve） compared with CSF-TPPA, CSF-FTA-ABS or CSF protein quantification. Key words: Neurosyphilis; Syphilis serodiagnosis; Sensitivity and specificity; Area under curve