Re-evaluation of serological criteria for early syphilis treatment efficacy: progression to neurosyphilis despite therapy.

OBJECTIVES: To study 17 cases of secondary syphilis that progressed to neurosyphilis despite appropriate treatments and whose rapid plasma reagin (RPR) titres showed a fourfold decrease within 6 months but did not revert to negative.

METHODS: Secondary syphilis patients with the following criteria were analysed: (1) RPR titres declined fourfold within 3 months after therapy, (2) patients denied high-risk sexual behaviours following treatment, (3) RPR titre remained serofast 24 months after treatment, (4) reactive cerebrospinal fluid (CSF)-venereal disease research laboratory (VDRL) and CSF-Treponema pallidum Particle Agglutination Test (TPPA) and (5) HIV antibody negative.

RESULTS: 14 male and three female patients met the criteria. 13 patients were asymptomatic. The CSF leucocyte count was elevated in 10 patients of whom nine also had elevated CSF-proteins. The RPR titres following secondary syphilis treatments were ≥ 1:32 in five cases, 1:16 in four cases, 1:8 in six cases and 1:4 in two cases. Following treatments for neurosyphilis, four cases with neurological or psychiatric manifestations resolved or improved, nine cases with raised CSF-white blood cells returned to normal and nine of 12 cases with raised CSF-protein declined to normal.

CONCLUSIONS: Neurosyphilis may be detected in immunocompetent patients despite appropriate therapy for early-stage syphilis and appropriate serological responses. Clinicians should consider a CSF examination in any treated patient with evidence of disease progression irrespective of prior treatment history and serological response.