Implementation and Innovation in Syphilis Diagnostics: Insights from Global Health Systems, Molecular Testing, and Self-Testing Strategies

Abstract

Background:

Syphilis remains a persistent global public health problem. Given that low-cost diagnostics and highly effective therapies have been available for decades, the current epidemic is driven by structural weaknesses in health systems, stigma, absence of political will and failures to integrate new technologies into routine care.

Methods:

At the Shanghai 2025 Syphilis Meeting, experts highlighted the evolving landscape of syphilis diagnostics. The presentations offered an overview of our changing understanding of seronegative primary disease, reinfection patterns, and asymptomatic mucosal shedding as well as the limitations of diagnostics for neurosyphilis and novel approaches that have shown promising performance.

Results:

One presentation provided new insights into congenital syphilis by demonstrating significant changes seen on fetal ultrasound and compelling data suggesting a role for new point-of-care IgM tests for risk stratification of exposed newborns. Self-testing was highlighted as an emerging strategy that leverages community engagement, decentralization, and digital technologies to reach populations historically excluded from facility-based services. Finally, a global systems-level overview offered a summary of implementation barriers for diagnostic assays, the need for sustainable adoption of point-of-care tests, and the policy deficits that impede progress.

Conclusion:

The presentations collectively illustrated the complex interplay between technology, systems design, behavioral dynamics, and policy in shaping the global response to syphilis. The path forward requires an approach that integrates novel diagnostic and digital technologies with programs designed to strengthen health systems as well as community partnerships. Such cross-disciplinary frameworks have the potential to reduce diagnostic inequities and accelerate progress toward the elimination of syphilis worldwide.

Syphilis remains a persistent global public health problem. The World Health Organization estimated that more than 8 million new infections occured in 2020.¹ Syphilis causes stillbirth, congenital infection, neonatal death, neurosyphilis, and other long-term complications in adults. Low-cost diagnostics and highly effective therapies for syphilis have been available for decades. Thus, the global syphilis epidemic is the result of structural weaknesses and fragmentation in health systems as well as the absence of political will leading to a lack of routine testing, access to care, and treatment.^2,3 That is further compounded by stigma around the disease, homophobia, and transphobia, while failures to integrate new technologies into routine care continue to hinder progress.^4,5 Those challenges are particularly pronounced in low-resource settings, where access to basic laboratory testing remains uneven, and health system fragmentation frequently undermines timely diagnosis and treatment.^4,5 In addition, syphilis can be asymptomatic and current diagnostic tests often fail to distinguish past from present infections, leading to missed cases and inappropriate treatment.

The presentations at the Shanghai 2025 Syphilis Meeting, which took place October 23 to 27, 2025, highlighted the evolving landscape of syphilis diagnostics. Towns presented 2 decades of laboratory experience with molecular diagnostics that may reshape our understanding of the clinical and epidemiologic features of early syphilis, especially with respect to seronegative primary disease, reinfection patterns, and asymptomatic mucosal shedding.^6–8 Ye reviewed the current limitations in neurosyphilis diagnostics and therapeutics and presented promising data on the performance of a new molecular assay.^9–11 Stafford offered new insights into fetal disease by demonstrating critical decreases in fetal long bone length and estimated fetal weight among exposed fetuses during pregnancy. She also presented compelling data suggesting a role for new point-of-care IgM tests in risk stratification for exposed newborns.¹² Wang offered an in-depth examination of syphilis self-testing as an emerging strategy that leverages community engagement, decentralization, and digital technologies to reach populations historically excluded from facility-based services. He presented extensive evidence from randomized trials and pragmatic implementation studies in China.^13–17 Peeling provided a global systems-level overview of implementation barriers for diagnostic assays, the pathways required for sustainable adoption of rapid point-of-care diagnostics, and the policy deficits that impede progress. Peeling further contextualized diagnostic innovations within the broader needs of health system strengthening, quality assurance, supply chain stability, and multisectoral governance.

Together, those presentations demonstrated how advances in technology, whether molecular assays, rapid point-of-care tests, or self-testing kits, must be accompanied by corresponding innovations in systems design, policy, financing, and community engagement. The following synthesis summarizes the key themes across the presentations and reviews the scientific evidence and implementation lessons that will shape the next decade of syphilis control efforts.

MOLECULAR DIAGNOSTICS AND NEW INSIGHTS INTO EARLY AND RECURRENT SYPHILIS

Towns' presentation offered an extensive examination of molecular nucleic acid testing and its role in redefining the diagnostic boundaries of early syphilis. Building upon more than 2 decades of experience with polymerase chain reaction (PCR) assays at the Victorian Infectious Diseases Reference Laboratory, she documented how molecular testing has revealed complexities in clinical presentation and serologic response that were previously underappreciated. Her findings demonstrated that classical descriptions of primary syphilis—typically characterized by a single painless chancre—represent only a subset of real-world presentations. In a large cohort of 183 individuals with PCR-confirmed primary anogenital lesions, she observed that nearly half of the cases involved painful lesions and more than one-third involved multiple lesions. Importantly, approximately one-fifth of those cases had nonreactive rapid plasma reagin tests despite positive treponemal serology and positive PCR results, emphasizing the limitations of relying on lipoidal (nontreponemal) tests for early diagnosis.⁶

Towns further highlighted the phenomenon of seronegative primary syphilis, which has significant implications for public health surveillance and clinical management. In her 2022 analysis of more than 800 primary syphilis cases, 4.7% had negative treponemal and lipoidal serologic tests at presentation despite PCR positivity.⁷ Those individuals generally presented with very recent lesions, with a median symptom duration of only 3 days. When early treatment was provided, particularly on the first day of clinical presentation, seroconversion was less-likely to occur at follow-up. That finding suggests that treatment administered before humoral responses develop may prevent expected serologic patterns, thereby complicating the interpretation of treatment success and serologic monitoring. A systematic review conducted with Hughes et al.⁸ further indicated that approximately 10% of PCR-positive primary infections could be missed if diagnosis relied solely on serology, reinforcing the value of molecular diagnostics in early disease detection.

Towns also described the challenges of diagnosing reinfection among people with a history of syphilis. In a cohort of 474 patients with multiple documented infections, the study team identified frequent discordance among treponemal and lipoidal assays at the time of reinfection.¹⁸ For example, more than 20% of primary-stage reinfections were characterized by nonreactive rapid plasma reagin results, and a substantial proportion failed to demonstrate the 4-fold rise typically used to indicate a new infection. Those findings suggest that traditional serologic criteria may be insufficiently sensitive for identifying reinfection in high-incidence populations, particularly when people are repeatedly exposed or treated early.

Beyond lesion-based diagnostics, Towns examined mucosal detection of Treponema pallidum DNA in oral, rectal, urinary, and semen specimens.¹⁹ She presented data showing that DNA can be detected in multiple specimen types from multiple anatomic sites, including in mucosal specimens in those without visible ulcers. In oral rinse specimens, approximately one-quarter of early syphilis cases were PCR-positive even in the absence of oral lesions, and oral mucosal detection rates approached 50% in those with secondary syphilis. Similar patterns occurred in pharyngeal and anal swabs, where substantial proportions of individuals without visible mucosal abnormalities nonetheless exhibited detectable T. pallidum DNA.^20–23 The variability in sampling methods, PCR targets, and cohort characteristics across studies complicates interpretation, but the overall pattern supports the role that asymptomatic mucosal shedding might play in the transmission of syphilis.

Towns noted that nucleic acid detection alone does not prove organism viability or infectiousness. Methods such as dark-field microscopy and rabbit infectivity testing are too labor-, cost-, and time-intensive for routine use. Novel molecular assays are in development that establish viability either through direct detection of T. pallidum proteases, an intercalating dye that prevents amplification of extracellular (nonviable) nucleic acids, or via quantification of the ratio between mRNA and DNA; while those methods are not available for routine use, they may provide platforms for investigating infectiousness of the T. pallidum DNA detected at asymptomatic mucosal sites. Nevertheless, her data strongly supported the need for additional research on the role of asymptomatic mucosal shedding in transmission, the development of improved molecular tools, and standardized sampling protocols that maximize assay sensitivity.

IMPROVED DIAGNOSTICS FOR NEUROSYPHILIS

Ye provided an overview of neurosyphilis, which can occur at any stage of infection, ranging from asymptomatic cerebrospinal fluid abnormalities to severe, irreversible neurological dysfunction. Evidence from cohort and cross-sectional studies demonstrated high rates of misdiagnosis and prolonged diagnostic delays, frequently resulting in preventable morbidity.^9–11 Current diagnostic approaches lack unified international criteria and rely on imperfect integration of clinical features, serology, and cerebrospinal fluid testing, each with significant limitations in sensitivity and/or specificity. The presentation emphasized the importance of integrating historical insights with contemporary epidemiological, diagnostic, and therapeutic advances to tackle the rising rates of neurosyphilis.

Ye presented preliminary data demonstrating substantial improvements in PCR testing sensitivity in cerebrospinal fluid using an assay targeting multiple-copy fragment regions of the genome. The presentation also reviewed gaps in the current therapeutic paradigm; although penicillin remains the cornerstone of treatment, optimal dosing, duration, and follow-up strategies are not well standardized.²⁴ Further, residual neurological or psychiatric sequelae may persist in up to 40% of patients who received standard antibiotic therapy.

FETAL INFECTION AND NOVEL STRATEGIES FOR NEONATAL RISK STRATIFICATION

Stafford presented findings on novel diagnostic approaches for congenital syphilis. The presentation described the preliminary results of a prospective cohort study that examined ultrasounds of over 64 fetuses exposed to syphilis. Those data illustrated significant decreases in growth velocity across sequential ultrasound evaluations, with a nearly 3-fold increase in fetal growth restriction and significant decreases in long bone measurements over time, particularly for the fetal femur. Stafford suggested that such data can supplement existing protocols for congenital syphilis evaluation and diagnosis, particularly given the lack of a gold-standard diagnostic test for neonatal disease.

Stafford also presented results from a study evaluating the performance of 2 point-of-care IgM tests for congenital syphilis risk stratification. The first was published work illustrating the strong positive and negative percent agreement of the Syphilis Health Check point-of-care IgM (Diagnostics Direct, Stone Harbor, NJ) with a composite IgM reference comparator (positive percent agreement 93% (95% confidence interval [CI], 68.0%–99.8%, negative percent agreement (95% CI, 87.5%–97.3%), as well as with clinical congenital syphilis categories (less-likely, possible, and highly probable/confirmed congenital syphilis), where positive percent agreement and negative percent agreement were 100% (95% CI, 73.5%–100%) and 82% (95% CI, 61.9%–93.7%), respectively, for 29 mother-newborn dyads.¹²

The test performance of another novel point-of-care test, the DPP Syphilis Screen and Confirm (ChemBio Diagnostics Inc., Medford, NY) for IgM antibody detection, was also evaluated in 21 neonates at risk for congenital syphilis. That point-of-care test measures treponemal and lipoidal (nontreponemal) IgM antibodies. Treponemal IgM levels differed significantly across congenital syphilis categories (less-likely, possible, and highly probable/confirmed), with increasing fluorescence values on an electronic reader demonstrating a clear overall association with increasing disease likelihood. Those findings suggest that neonatal treponemal IgM may serve as a rapid screening test to rule out congenital syphilis, and tests with high fluorescence values might identify infants with possible, or highly probable/confirmed congenital syphilis.

SYPHILIS SELF-TESTING AND DECENTRALIZED DIAGNOSTIC STRATEGIES IN CHINA

Wang’s presentation situated syphilis self-testing within the World Health Organization’s sexually transmitted infection strategy and its 2025 syphilis self-testing implementation guideline.¹³ Syphilis self-testing was framed as a critical innovation capable of addressing longstanding barriers associated with facility-based testing, including stigma, inconvenience, limited autonomy, and geographic inaccessibility. The conceptual framework described a continuum from centralized facility-based testing to decentralized point-of-care testing and ultimately to self-administered testing.

Wang presented a series of studies^14,15 that illustrated the acceptability, feasibility, and impact of syphilis self-testing among key populations, particularly men who have sex with men and female sex workers. In a national online survey of nearly 700 men across 103 Chinese cities, approximately one-quarter had previously used syphilis self-testing. Among those withreactive or indeterminate test results, more than 80% sought follow-up medical evaluation.¹⁴ Notably, more than half of people who used syphilis self-testing reported that it had been their first-ever syphilis test.

Randomized controlled trials conducted by Wang et al. provided rigorous evidence that syphilis self-testing markedly increased testing uptake. In one multiarm trial involving 451 men who have sex with men, participants randomized to receive syphilis self-testing kits demonstrated testing uptake rates exceeding 60%, compared with only 15% in the standard-of-care arm.¹⁶ The inclusion of a lottery-based incentive further increased testing frequency. Importantly, all newly identified syphilis cases across the syphilis self-testing arms successfully accessed follow-up testing and treatment, although syphilis stage was not reported.

A pragmatic randomized controlled trial evaluating social network distribution demonstrated that providing individuals with syphilis self-testing kits to distribute to peers led to significant increases in the number of people tested.¹⁷ Nearly half of those who used syphilis self-testing were first-time testers, underscoring the importance of leveraging social connections to extend the reach of testing into hidden populations.

In summarizing global evidence, Wang noted that treponemal syphilis self-testing generally shows excellent specificity and variable but clinically acceptable sensitivity. Given self-tests are predominantly based on treponemal antibodies, additional testing may still be required to detect current infection among people with a history of previous treatment for syphilis. Acceptability was consistently high across settings, driven by privacy, convenience, and autonomy. Syphilis self-testing repeatedly demonstrated its ability to increase both overall testing and first-time testing rates.^16,17 Economic evaluations suggested that syphilis self-testing is cost-effective in moderate-to-high prevalence settings when linkage-to-treatment rates exceed 70%.^16,25,26

GLOBAL HEALTH SYSTEM CHALLENGES AND THE IMPLEMENTATION OF RAPID SYPHILIS DIAGNOSTICS

Peeling described a landscape in which syphilis diagnostics, although technologically mature, remain grossly underutilized because of profound gaps across health systems. In many low-resource settings, diagnostic access is constrained by inadequate laboratory capacity, frequent stockouts, personnel shortages, and inconsistent adherence to national guidelines. Those systemic deficiencies are compounded by patient- and community-level barriers such as limited health literacy, long travel distances, stigma surrounding sexually transmitted infections, and unaffordable user fees. The combined effect is that syphilis testing is far less consistently provided than HIV testing, even in the same clinical settings. For example, while some countries achieve HIV antenatal screening coverage of approximately 95%, far fewer pregnant women are screened for syphilis.²⁷ Among 81 countries that account for more than 90% of under-5 child deaths, only 65% included maternal syphilis testing and less than half included maternal syphilis treatment²⁸ despite the disproportionate risk that untreated maternal infection poses to fetal and neonatal health.

Peeling emphasized that the implementation of rapid syphilis tests has often required substantial investments in policy development, regulatory evaluation, training, workflow redesign, procurement, and monitoring systems. Her presentation illustrated how syphilis “falls between the cracks” of multiple clinical programs, including maternal and child health, reproductive health, sexually transmitted infection clinics, and laboratory departments. That fragmentation delays decision-making and undermines coordinated resource allocation. To address those challenges, Peeling outlined a structured framework that supports sustained adoption of rapid diagnostics, which includes raising awareness among clinicians and policymakers, evaluating candidate tests in both laboratory and clinical settings, developing consensus around test selection and algorithms, ensuring consistent procurement and stock management, conducting extensive training and training-of-trainers programs, establishing quality control and external quality assessment processes, and linking screening activities to surveillance systems capable of evaluating population-level impact.

Case studies, such as implementation initiatives in Peru, China, and Haiti, illustrated the transformative potential of point-of-care testing when it is successfully integrated into routine workflows.²⁹ In Peru, for instance, a striking comparison between pre- and post-point-of-care testing antenatal pathways demonstrated that a process previously requiring multiple visits, venous blood collection, and delayed results could be replaced by a single-visit model in which HIV and syphilis results from one finger-stick sample were available immediately, enabling same-day treatment and partner notification.³⁰ Another example in Haiti demonstrated that point-of-care testing alone was insufficient to maximize treatment rates. Only when rapid diagnostics were combined with systems-based quality improvement interventions did treatment coverage improve.²⁷ That finding underscored Peeling’s central argument that new technologies—no matter how innovative—cannot reach their potential without corresponding investments in the systems needed to deliver them reliably.

Peeling also highlighted the broader global challenge of diagnostic neglect. Drawing upon findings from the 2021 Lancet Commission on Diagnostics,⁵ she noted that nearly half of the world’s population has inadequate access to essential diagnostic tools. Syphilis is explicitly included among 6 high-impact conditions for which closing the diagnostic gap could prevent more than one million premature deaths annually. Investments made during the COVID-19 pandemic, particularly those enhancing supply chains, laboratory networks, regulatory systems, and regional manufacturing capacity, offer opportunities to accelerate the expansion of syphilis testing if leveraged strategically. Moreover, she underscored the importance of digital connectivity, both for real-time surveillance and for quality assurance programs that rely on remote data transmission supported by mobile health technologies.

Peeling emphasized the need to bridge the technology-to-systems gap. She argued that successful diagnostic implementation requires more than the distribution of test kits; it requires system-wide coordination across political, financial, logistical, and community-level domains. Mapping the syphilis screen-and-treat pathway is essential for identifying bottlenecks and determining where rapid testing or self-testing could simplify workflows. Understanding social and cultural contexts is equally important for overcoming stigma and designing effective health messaging.

FUTURE DIRECTIONS

The presentations collectively highlighted several domains where future efforts could meaningfully strengthen syphilis diagnostic capacity and improve health outcomes. One priority is the consolidation of diagnostic services across historically siloed programs; for example, despite widely available and cost-effective dual HIV-syphilis tests,²⁵ vertical HIV programs often exclusively test for HIV.²⁷ Future strategies must include harmonized procurement, coordinated financing, and integrated reporting platforms.

Advances in molecular diagnostics create new possibilities for earlier and more accurate detection. Towns underscored the need for studies that evaluate molecular screening in high-incidence populations. Research is needed to better understand mucosal shedding and its role in transmission. The development of assays capable of detecting viable organisms would address longstanding questions regarding infectiousness.

Self-testing represents another area with substantial potential for innovation. Future test development should prioritize assays that distinguish current versus past infection, simplified interfaces, and nonblood-based sampling. Implementation research is required to evaluate syphilis self-testing in additional populations, including pregnant women, migrants, transgender people, and adolescents.

Health system resilience was a recurring theme across the presentations. Increasing access to diagnostics requires strengthening public health laboratories, establishing external quality assessment systems, and ensuring stable procurement channels. Investments in regional manufacturing capacity and regulatory harmonization would reduce reliance on unstable supply chains. Underpinning those efforts, community engagement must remain central, which could be supported by pay-it-forward models and/or crowdsourced campaigns.

CONCLUSIONS

The presentations synthesized in this report collectively illustrated the complex interplay between technology, systems design, behavioral dynamics, and policy in shaping the global response to syphilis. The path forward requires a holistic approach that integrates diagnostic and information technologies with strengthening health systems and community partnership. Such cross-disciplinary and integrated frameworks have the potential to meaningfully reduce the diagnostic equity gap and accelerate progress toward the elimination of syphilis worldwide.