A Potential Screening Strategy to Identify Probable Syphilis Infections in the Urban Emergency Department Setting

Syphilis diagnosis in the emergency department (ED) setting is often missed due to the lack of ED-specific testing strategies. We characterized ED patients with high-titer syphilis infections (HTSIs) with the goal of defining a screening strategy that most parsimoniously identifies undiagnosed, untreated syphilis infections.

Unlinked, de-identified remnant serum samples from patients attending an urban ED, between 10 January and 9 February 2022, were tested using a three-tier testing algorithm, and sociodemographic variables were extracted from ED administrative database prior to testing. Patients who tested positive for treponemal antibodies in the first tier and positive at high titer (≥1:8) for nontreponemal antibodies in the second tier were classified as HTSI. Human immunodeficiency virus (HIV) status was determined with Bio-Rad enzyme-linked immunosorbent assay and confirmatory assays. Exact logistic regression and classification and regression tree (CART) analyses were performed to determine factors associated with HTSI and derive screening strategies.

Among 1951 unique patients tested, 23 (1.2% [95% confidence interval, .8%-1.8%]) had HTSI. Of those, 18 (78%) lacked a primary care physician, 5 (22%) were HIV positive, and 8 (35%) were women of reproductive age (18-49 years). CART analysis (area under the curve of 0.67) showed that using a screening strategy that measured syphilis antibodies in patients with HIV, without a primary care physician, and women of reproductive age would have identified most patients with HTSI (21/23 [91%]).

We show a high prevalence of HTSI in an urban ED and propose a feasible, novel screening strategy to curtail community transmission and prevent long-term complications.