Novel and Effective Approach to Reducing Syphilis Among Gay and Bisexual Men Who Have Sex With Men Using Anorectal Digital Self-examination

The ongoing syphilis epidemic over the last 2 decades has been associated with the highest rates of disease reported since the 1950s [1, 2]. Syphilis can lead to high morbidity including neurological, ocular, and otosyphilis; increased risk of human immunodeficiency virus acquisition [3]; and congenital syphilis, with the highest incidence of perinatal syphilis in more than 30 years reported in North America, Europe, and Australia in 2022–2023 [1, 4–6]. The World Health Organization established the goal of reducing the incidence of new cases of syphilis among people 15–49 years old per year by 90% within 10 years, from an estimated 7.1 million cases in 2020 to 0.71 million cases in 2030 [7]. A priority of these efforts includes supporting gay, bisexual, and other men who have sex with men (GBMSM) who are disproportionately affected by syphilis [8]. Infectious syphilis can often be asymptomatic or associated with mild or nonspecific symptoms. As a result, 1 of the core public health strategies has been early detection. To date, this has focused on frequent, rapid, and accessible syphilis testing, particularly among individuals at highest risk [9]. Approaches include more accessible methods of sample collection and portable testing platforms, integration of health services and reminders to support more frequent testing, and delivery of testing services to a broader range of settings. Among the models that have shown the greatest promise thus far to increase the early detection of syphilis among GBMSM are pairing syphilis screening with regular clinical visits in the outpatient or emergency room setting using laboratory-based serology testing [10, 11], access to point-of-care testing [12], polymerase chain reaction–based testing [13], home testing [14], partner notifications, and web-based campaigns [15]. All of these strategies enable the detection of new incident cases of syphilis at varying rates, but studies of these approaches have not consistently integrated cost-effectiveness and public health effectiveness data. The study presented by Lai and colleagues in this issue of The Journal of Infectious Diseases [16] models the efficacy and cost-effectiveness of a novel approach for early detection of primary anorectal syphilis in GBMSM through self–digital rectal examination, or self-DARE, to reduce the transmission of syphilis. Primary syphilis involves the development of a painless chancre that develops at the initial site of inoculation within the first 30 days of infection. As anorectal chancres are not visible, individuals with infection secondary to anorectal exposure to syphilis often go undetected [17], increasing the risk of progressing to secondary and early latent syphilis, long-term sequelae, and the duration of time that they can transmit syphilis to others. The research team developed an integrated model of transmission dynamics and health economics using Australian incidence data of syphilis among GBMSM from 2012 to 2022. Estimating the impact of self-DARE on syphilis incidence among GBMSM in Australia for 2025–2034, their model examined the introduction of self-DARE using 2 strategies: (1) focused on GBMSM with 10 or more sexual partners per year (“only high group”) and (2) the introduction of self-DARE for all GBMSM (“both groups”). The model assumed a 180-day intervention duration, a self-DARE screening frequency of once every 30 days, and a sensitivity and specificity of 60% and 80% based on their previous studies. Parameters for duration of disease state, transmission, progression rates, testing frequency, and immunity (or lack thereof) after infection were based on available literature. Modeled costs included fees for clinician consultations and visits, testing and treatment based on stage of investigation and disease, linkage to care for self-DARE at 50 Australian dollars (A$) per person, and additional costs prompted by self-DARE findings and the quality-adjusted life-years of 0.6 per syphilis infection. A sensitivity analysis included variation in self-DARE uptake, frequency of self-testing, and variations in sensitivity and specificity of self-DARE for the detection of primary syphilis among the “only high group” and high- and low-frequency partner change groups, titled “both groups.” Their model supported the effectiveness of self-DARE in reducing new syphilis infections, with substantial reductions in new syphilis infections using both strategies. The “only high group” strategy reduced the projected new cases of syphilis by 51.7% (57 115 of 110 501 cases), and the “both groups” strategy reduced new cases of syphilis by 52.7% (58 216 cases). Both strategies were also found to be cost-effective, with incremental cost-effectiveness ratio of A$−9218.10 for the “only high group” and A$−9007.20 for “both groups.” The cost of averting a case of 1 new syphilis infection at A$292.3 in the “only high group” is below the cost of diagnosing and treating 1 early syphilis case (A$325). Given the relatively similar number of new infections averted using the “both group” compared to the “only high group” strategy and the associated increased costs of linkage to care and workup of possible lesions, the cost per case averted in the “both group” strategy was more than twice this cost at A$709.80 per new infection averted. Not only did this study support both the effectiveness and reduced cost of the self-DARE approach among the “only high group,” this team considers the implementation of the self-DARE strategy [9, 16, 18, 19]. This includes an increase in 5 syphilis tests per 1000 for the “only high group” and over 11 per 1000 for the “both groups” strategy. Associated with the identified increase in syphilis testing prompted by the model, the authors factor in the number and cost of clinical consultation for the primary diagnosis, confirmation, and treatment. Last, this approach enables self-efficacy compared to other screening methods. The acceptability and adherence of self-DARE for the detection of anal cancer and syphilis is well supported [18–21]. In a survey of 568 men who have sex with men, 32% had previously performed self-DARE, and 68% of the other 374 individuals who had never performed self-DARE would consider performing self-DARE in the future. In a study by the same team in 2020–2021, 30 men performed self-DARE at least weekly for 308 of 360 person-weeks during a 12-week period [18]. While adherence remained high throughout, there was a trend to reduced frequency with a mean of 3.6 self-examinations in the first 4 weeks to 3.3 self-examinations in the last 4 weeks. Using self-DARE, anorectal abnormalities were identified in 14 of 30 men, but only 6 of these prompted medical attention; none of the participants were diagnosed with syphilis in this study. The goal for reducing new cases of syphilis by 90% set out by the World Health Organization is ambitious and necessary to curb the overall burden worldwide, and critical to any pursuit of eradication. As described by Lai and colleagues, implementation of a self-DARE strategy among GBMSM with multiple sexual partners is promising and may be able to reduce the incidence of new cases of syphilis among GBMSM by up to 51.7%, is cost-effective, and can be implemented with minimal additional infrastructure. However, this strategy will have to be implemented in tandem with complementary public health approaches to meet international goals of syphilis control. Financial support. No financial support provided.

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