A-180 A Retrospective Review of Syphilis Serology Interpretation Accuracy
Authors: Forsythe M , Lee H K , Benirschke R C 
Published: September 2023

Abstract

Background
Syphilis is a sexually transmitted disease caused by the spirochaete bacterium Treponema pallidum. It is acquired through direct contact, is highly infectious and can survive in an untreated host for years. Multiple tests are available for diagnosis and broadly classified as treponemal and nontreponemal. Treponemal tests are used to detect T. pallidum particles and antibodies and the nontreponemal tests include the rapid plasma regain (RPR). Due to this complexity, interpreting syphilis serology tests are a common cause of questions to clinical consultants and have the potential for incorrect diagnosis. Because of this we initiated a retrospective review of past positive serology results to assess provider accuracy in interpreting these tests.

Methods
The study cohort was composed of 108 patients from July—December 2021 that had at least one positive serology test. The assays used were the Syphilis Total Antibodies and RPR assays and both were performed in-house. The clinical history of each patient was reviewed to obtain relevant data pertaining to the diagnosis. This information included the age, gender, additional send out confirmatory testing, previous history of syphilis, provider type and specialty who ordered the tests. The interpretation by the clinicians was also determined and whether they prescribed antibiotics. Statistical analysis was performed to assess what patient and provider characteristics were associated with a correct or incorrect interpretation of the syphilis test results. This study was approved by the institutional IRB.

Results
The study cohort showed that 12/108 (11.1%) positive results were interpreted incorrectly. The comparison of correct vs incorrect interpretation was insignificant across most of the variables, including age, gender, diagnosis and provider type. However, in relation to provider specialty the comparison was significant with a P-value of 0.003. This was due to a high percentage of incorrect interpretations obtained from family medicine providers, reaching roughly 50% of total incorrect interpretations. Empirically, questions to the Pathology laboratory concerning syphilis results interpretation have also been observed more often among the family medicine providers. Additionally, providers from infectious disease, internal medicine and OB/GYN composed 54.3% of the providers in our study and only had one interpretation error indicating very high accuracy.

Conclusion
Overall, the study demonstrated a significant number of incorrectly interpreted syphilis results, with the majority occurring among the family medicine providers. Assistance with interpretation of syphilis results is one of the most frequently asked questions received at the Pathology laboratory. Appropriate education, in particular for the family medicine providers, will assist in addressing this issue, as well as implementing additional resources to the electronic medical record that can be linked to the reported syphilis results. The distinction of a true positive diagnosis from a false one is important for proper patient care, preventing the treatment of patients who don’t need it and allowing for the timely treatment of those who do.