Submission ID 131812
| Issue/Objective | The gold standard for treatment of neurosyphilis historically is aqueous crystalline penicillin G (4 million units intravenously every 4 hours for 10-14 days); however, it is not conducive to ambulatory care due to the frequency of dosing or those with penicillin allergies. In Alberta, this product has been removed from home parenteral therapy (HPT) programs, creating a need for appropriate alternate treatment options. Ceftriaxone (2 grams intravenously once daily for 10-14 days) is recommended as an appropriate alternative in provincial and international guidelines. Despite current evidence, population-level evidence comparing serologic outcomes remains sparse, especially for key populations, such as people living with HIV (PLWHIV), pregnant individuals and those who are unhoused. This study aims to compare the serological response to treatment with ceftriaxone to crystalline penicillin G. |
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| Methodology/Approach | This is a retrospective cohort study, using clinical, laboratory and treatment data from Alberta's Communicable Disease/Outbreak Management (CDOM) database. All individuals staged with early or late neurosyphilis in Alberta between 2020 and 2024, with a treatment of either ceftriaxone or penicillin, for 10 or 14 days, with available follow-up serology are included. The primary outcome is serological response, defined by a ≥4-fold decrease in rapid plasma reagin (RPR) titer from the pre-treatment RPR to post-treatment RPR at 6, 12, and 24 months. Time-to-first ≥4-fold decline will be evaluated. Secondary outcomes include length of hospital stay and treatment failure between the treatment groups. |
| Results | 290 records will be analyzed, with 10% of these including PLWHIV. Baseline characteristics will be summarized by treatment group using descriptive statistics. Proportions achieving serologic response will be calculated at each follow-up interval, and time-to-event analyses using Cox proportional hazards models will estimate adjusted hazard ratios comparing ceftriaxone and penicillin G, with regression-based analyses adjusting for predetermined confounders, including age, gender, and HIV status. Prespecified subgroup analyses will be conducted for those who are pregnant, living with HIV, or unhoused. |
| Discussion/Conclusion | This study will add to the limited population-based evidence on the comparative serologic effectiveness of ceftriaxone and aqueous crystalline penicillin G for neurosyphilis treatment, informing clinical decision-making for HPT and provincial program development. |
| Presenters and Affiliations | Zara Ahmed University of Alberta Jennifer Gratrix Alberta Health Services Petra Smyczek Alberta Health Services Angel Chu Cumming School of Medicine, University of Calgary Caley Shukalek Cumming School of Medicine, University of Calgary Ameeta Singh Faculty of Medicine and Dentistry, University of Alberta Rabia Ahmed Faculty of Medicine and Dentistry, University of Alberta |
