The Estimated Lifetime Medical Cost of Syphilis in the United States

Background The purpose of this study was to estimate the cost of syphilis in the United States, in terms of the average lifetime direct medical cost per infection. Methods We used a decision tree model of the natural history of syphilis. The model allowed for numerous possible outcomes of infection, including treatment for syphilis at various stages, inadvertent treatment, and late syphilis outcomes in those who are alive and still infected 30 years after acquisition. Future costs were discounted at 3% annually. Model inputs, such as the cost and probability of each outcome, were based on published sources. The probabilities we applied yielded outcomes consistent with reported cases of syphilis by stage from national surveillance data and number of deaths due to late syphilis from national mortality data. Results The estimated, discounted lifetime cost per infection was $1190 under base case assumptions (2019 dollars). Treatment costs associated with late syphilis outcomes, such as cardiovascular syphilis, accounted for only $26 of the average lifetime cost per infection. Results were most sensitive to assumptions regarding the treatment cost per case of unknown duration or late syphilis. In the probabilistic sensitivity analyses, the 2.5th and 97.5th percentiles of the 10,000 simulations of the lifetime cost per infection were $729 and $1884, respectively. Conclusions Our estimate of the lifetime cost per infection is about 50% higher than in a previous study, a difference due in large part to our higher cost assumptions for benzathine penicillin G.