The performance of rapid plasma reagin (RPR) titer in HIV-negative general paresis after neurosyphilis therapy

Background Repeated nontreponemal serologic test for syphilis titers is recommended to evaluate treatment response. However, it is unknown whether serum rapid plasma reagin (RPR) titer can serve as a surrogate for determining the efficacy of treatment in general paresis (GP) remains unknown. Methods We retrospectively reviewed data from 105 GP patients, who were divided into two groups (62 CSF RPR+ patients and 43 CSF RPR- patients) according to reactive RPR test status in CSF. Clinical assessment included the Mini-Mental State Examination (MMSE) scores, CSF examinations (WBC count, protein concentration and RPR titer), and serum tests (RPR titer and TPPA). Among the 105 GP patients, 13 CSF RPR+ patients and 6 CSF RPR- patients had a 12 months follow-up of CSF, serum measures and MMSE. Results The median serum RPR titer was significantly higher in CSF RPR+ patients than that in CSF RPR- GP patients, 1:8 [IQR 1:4–1:32] vs. 1:4 [IQR 1:4–1:8] ( P < 0.001). The number of CSF RPR+ patients with serum RPR titer≥1:32 was significantly higher when compared with CSF RPR- patients ( P = 0.001). For CSF RPR+ patients, the MMSE scores improved or remained constantly after penicillin treatment. For CSF RPR+ patients, the CSF RPR titer declined four-fold in 85% (11/13) of the patients, whereas the serum RPR titer declined four-fold in only 46% (6/13) of the patients, the odds ratio is 6.4 (95% confidence interval 1.0–41.2). Conclusions A four-fold decline in CSF RPR titer is a good predictor for treatment efficacy in CSF RPR+ GP patients within 12 months after the completion of therapy.