Serological response to therapy following retreatment of serofast early syphilis patients with benzathine penicillin.

Background: Some syphilitic patients remain in a serologically positive state after the recommended therapy. Although we often retreat patients in clinical practice, the optimal treatment protocol remains uncertain due to the paucity of data regarding serological response to retreatment and long-term outcomes. Methods: We examined rapid plasma reagin serological test results of 70 serofast early syphilis cases who were retreated with 2.4 million units of benzathine penicillin weekly for 3 weeks. Serological retreatment success was defined as a minimum 4-fold decrease in baseline rapid plasma reagin test antibody titre within 6 months. Results: Thirty-four (48.6%) of the patients who failed to achieve serological cure at 6 months after initial therapy achieved serological cure at 12 months. Patients who had higher non-treponemal titres at baseline and at 6 months were more likely to exhibit serological cure after retreatment than those with lower titres. Conclusions: Our results suggest that the incremental benefit of retreating serofast patients with early syphilis is moderate, considering the almost 1:1 ratio of serological response to serofast state at follow-up.