(380) Cost-effectiveness of a reverse screening algorithm for syphilis in pregnancy

Syphilis rates in the U.S. continue to rise from historic lows in 2000. In pregnancy, it is crucial to screen and diagnose infection to prevent vertical transmission. Traditionally, screening is done with a non-treponemal test such as the rapid plasma reagin (RPR) followed by confirmatory testing using a treponemal immunoassay. The greater sensitivity of the immunoassays compared to non-treponemal tests has led to the emergence of a reverse screening algorithm (immunoassay followed by RPR), however they have lower specificity. Nationally, there is heterogeneity in the algorithm used. In this study, we evaluated the cost-effectiveness of syphilis screening in pregnancy using a traditional versus reverse screening algorithm. 

Study Design:

We constructed a decision-analytic model to compare outcomes between traditional and reverse screening. Our theoretical cohort included 3,408,000 individuals, the estimated annual live births among individuals without history of prior syphilis infection. Outcomes were stillbirth, preterm birth, infant death, congenital syphilis, undiagnosed syphilis cases, costs, and quality adjusted life years (QALYs). We used a willingness-to-pay for the incremental cost-effectiveness ratio of $100,000/QALY. Model inputs were derived from the literature and assessed with sensitivity analyses. 

Results:

In our cohort, the reverse screening approach was associated with 368 fewer cases of undiagnosed maternal syphilis infections, 50 fewer stillbirths, 17 fewer preterm births, 59 fewer infant deaths, and 67 fewer cases of congenital syphilis. Despite higher costs, reverse screening was cost-effective with an ICER of $8,328/QALY. In univariate sensitivity analysis, reverse screening was cost-saving when the immunoassay cost was below $5.48. 

Conclusion:

In our study, the reverse screening approach was a cost-effective strategy to improve diagnosis of syphilis in pregnancy and reduce adverse outcomes associated with vertical transfer. Adopting reverse screening protocols for pregnant individuals could be advantageous for health systems.