(286) Allergy evaluation in syphilis positive pregnant individuals with penicillin allergy: A cost effectiveness analysis

U.S. syphilis rates and vertical transmission have been increasing since 2001. The only treatment for syphilis in pregnancy is penicillin G (PCN). For those with a PCN allergy, no alternate antibiotics are effective, and they are recommended to be evaluated, desensitized if needed, and treated with PCN. Patients can either undergo allergy evaluation and risk stratification, or be directly desensitized at obstetric point of care. In this study, we evaluated allergy evaluation for PCN-allergic, syphilis-positive pregnant individuals as a means to prevent potential anaphylaxis with PCN exposure.

Study Design:

We constructed a decision-analytic model to compare outcomes between those who received an allergy evaluation and those who were directly desensitized. Our theoretical cohort was 600 patients, the estimated annual number of syphilis-positive pregnant individuals with a PCN allergy in the U.S. Outcomes were cost, quality-adjusted life years (QALY), anaphylaxis, preterm birth, stillbirth, neonatal death, and congenital syphilis. We set a cost-effectiveness threshold of $100,000/QALY. Model inputs were derived from literature and assessed using univariate sensitivity analyses.

Results: In our cohort of 600, allergy evaluation was associated with 6 fewer cases of anaphylaxis (18 vs 24), cost saving of $30,000, and 6 increased QALYs.  Allergy evaluation and direct desensitization were both associated with 62 preterm births, 31 stillbirths, 20 neonatal deaths, and 80 cases of congenital syphilis. In sensitivity analysis allergy evaluation remained cost effective until the cost of evaluation exceeded $1215.

Conclusion: Allergy evaluation and direct desensitization are both effective in facilitating syphilis treatment with PCN and preventing neonatal morbidity/mortality associated with vertical transmission. However, maternal anaphylaxis is less likely with allergy evaluation, and evaluation results in cost saving and QALY increase. Given that anaphylaxis can be a potentially life-threatening complication of pregnancy, allergy evaluation can be a beneficial resource for this population.