Point-of-Care Diagnostics for Diagnosis of Active Syphilis Infection: Needs, Challenges and the Way Forward

Two-Stage Syphilis Testing

A 54-year-old woman presented with erythematous annular and indurated plaques on her face, trunk, and extremities and had false-positive syphilis test results during 2 pregnancies 25 and 22 years prior. What would you do next?

The Epidemic of Congenital Syphilis in the Indigenous and Rural Populations of South Dakota

From 2020 to 2023, South Dakota witnessed a substantial increase in cases of congenital syphilis (CS), with the highest rates identified in rural and Native American (NA) communities. Here, we discuss 3 severe cases of CS in premature infants born to NA individuals and communities in South Dakota with poor access to prenatal care. The infants in these 3 cases presented with varying clinical conditions, including respiratory failure, persistent pulmonary hypertension of the newborn, severe direct hyperbilirubinemia, feeding intolerance, and necrotizing enterocolitis. Lack of prenatal care and other systemic health disparities likely contributed to the increased disease burden. For NA communities, rurality, limited resources, systemic racism, historical trauma, and lack of trust in medical institutions likely contribute to inadequate prenatal care. All 3 of these cases also occurred in pregnant people with a present or history of substance use disorders, which may have led to further hesitancy to seek care because of fear of prosecution. To combat the rising number of syphilis and CS cases, we advocate for new and continued outreach that provides education about and testing for sexually transmitted diseases to NA and rural populations, increased care coordination, the integration of point-of-care testing and treatment strategies in lower resource centers, and legislative allocation of additional resources to engage pregnant people with or at risk for substance use disorders.

On The Horizon: Novel Approaches to Sexually Transmitted Infection Prevention

Rates of sexually transmitted infections (STIs), especially cases of infectious and congenital syphilis, are increasing in the United States. Novel strategies for STI prevention are being explored and include doxycycline post-exposure prophylaxis and the potential utility of vaccines against gonorrhea. Self-collection of samples and point of care testing for STI are increasingly being employed in a variety of settings. Both can improve uptake of screening and lead to earlier detection and treatment of incident STI in target populations. Overcoming existing regulatory issues and optimizing implementation of current evidence-based strategies will be key to maximizing future STI prevention efforts. Here we provide an update for primary care providers on selected new strategies for STI prevention either currently available or under development for possible future use.

Evaluation of whole-genome enrichment and sequencing of T. pallidum from FFPE samples after 75 years

The recent developments in genomic sequencing have permitted the publication of many new complete genome sequences of Treponema pallidum pallidum, the bacterium responsible for syphilis, which has led to a new understanding of its phylogeny and diversity. However, few archived samples are available, because of the degradability of the bacterium and the difficulties in preservation. We present a complete genome obtained from a Formalin-Fixed Paraffin-Embedded (FFPE) organ sample from 1947, kept at the Strasbourg Faculty of Medicine. This is the preliminary, proof-of concept study of this collection/biobank of more than 1.5 million FFPE samples and the evaluation of the feasibility of genomic analyses. We demonstrate here that even degraded DNA from fragile bacteria can be recovered from 75-year-old FFPE samples and therefore propose that such collections as this one can function as sources of biological material for genetic studies of pathogens, cancer, or even the historical human population itself.

Research of Combined ES-BP Model in Predicting Syphilis Incidence 1982-2020 in Mainland China

Background

Syphilis remains a major public health concern in China. We aimed to construct an optimum model to forecast syphilis epidemic trends and provide effective precautionary measures for prevention and control.

Methods

Data on the incidence of syphilis between 1982 and 2020 were obtained from the China Health Statistics Yearbook. An exponential smoothing model (ES model) and a BP neural network model were constructed, and on this basis, the ES-BP combination model was created. The prediction performance was assessed to compare the MAE (Mean Absolute Error), MSE (Mean Squared Error), MAPE (Mean Absolute Percentage Error), and RMSE (Root Mean Square Error).

Results

The optimum ES model was Brown's linear trend model, which had the lowest MAE and MAPE values, and its residual was a white noise sequence (P=0.359). The optimum BP neural network model had three layers with the number of nodes in the input, hidden, and output layers set to 5, 11, and 1, and the mean values of MAE, MSE, and RMSE by five-fold cross-validation were 1.519, 6.894, and 1.969, respectively. The ES-BP combination model had three layers, with model nodes 1, 4, and 1. The lowest mean values of MAE, MSE, and RMSE obtained by five-fold cross-validation were 1.265, 5.739, and 2.105, respectively.

Conclusion

The ES, BP neural network, and ES-BP combination models can be used to predict syphilis incidence, but the prediction performance of the ES-BP combination model is better than that of a basic ES model and a basic BP neural network model.

Good performance of syphilis rapid diagnostic test kits among young key populations in Thailand

BACKGROUND

The prevalence of syphilis is increasing among adolescents and young adults (AYAs) globally. Use of syphilis rapid diagnostic treponemal tests (RDTs) may improve test coverage and same-day treatment. This study aims to determine sensitivity and specificity of two syphilis RDTs.

METHODS

A cross-sectional study was conducted in men who have sex with men and transgender women aged 15-24 years attending a sexual health clinic in Bangkok. Syphilis RDTs used were Determine Syphilis TP and Bioline Syphilis 3.0, using whole blood from finger pricks and venipuncture. Treponemal pallidum electrochemiluminescence assay was used as standard reference.

RESULTS

From February to July 2022, 200 AYAs with a mean age 21.1 (SD2.1) years were enrolled, including 50 (25.0%) living with HIV. Prevalence of syphilis was 10.5% (95%CI 6.6-15.6), which was higher among AYAs living with HIV (22.0%) compared with AYAs unaffected by HIV (6.7%). Sensitivities of Determine Syphilis TP and Bioline Syphilis 3.0 were 85.7% (95%CI 63.7-97.0) and 66.7% (95%CI 43.0-85.4), respectively. Specificity of both RDTs was 100% (95%CI 98.0-100.0). Performance of RDTs was similar for both specimens.

CONCLUSIONS

Syphilis RDTs have high sensitivity and specificity in diagnosing syphilis. It should be considered for use in sexual health clinics with high syphilis prevalence to initiate treatment promptly.

Advantages and limitations of current diagnostic laboratory approaches in syphilis and congenital syphilis

INTRODUCTION

The reemergence of syphilis, especially congenital syphilis, presents a significant public health threat. Accurate diagnosis of syphilis depends on recognition of a constellation of symptoms, review of medical and sexual history, and multiple laboratory tests. While reliable, current tests for syphilis can be difficult to interpret, which can lead to delays in treatment.

AREA COVERED

This review summarizes the major advantages and limitations of available diagnostic laboratory methods for syphilis, provides an update on recent advances in laboratory tools, and highlights the urgent need for coordinated efforts to create new tools to halt the resurgence of syphilis.

EXPERT OPINION

In syphilis, the wide variety of short-lived signs and symptoms followed by periods of latency create diagnostic challenges. Currently available laboratory tests, when positive, require additional information to interpret (prior testing, treatment, and sexual history). Point-of-care tests that can rapidly and accurately detect both treponemal and non-treponemal antibodies would be a huge step toward reducing test turnaround time and time to treatment. Incorporating biological insights and technology innovations to advance the development of direct detection assays is urgently needed. A comprehensive coordinated effort is critical to stem the tide of rising syphilis in the United States and globally.

Shifting the power: scale-up of access to point-of-care and self-testing for sexually transmitted infections in low-income and middle-income settings

PURPOSE OF REVIEW

Point-of-care (POC) testing for sexually transmitted infections (STIs) can provide complementary coverage to existing HIV testing services in LMICs. This review summarizes current and emerging technologies for detecting STIs in LMICs, with an emphasis on women, discharge-causing infections (chlamydia, gonorrhoea, trichomoniasis, and syphilis), true POC, self-testing, ethics, and economic considerations related to equitable access.

RECENT FINDINGS

The WHO have recently adapted guidelines for treatment of STIs in women that advise the use of true-POC or near-POC tests to improve case finding. The number of rapid, sensitive, and specific POC diagnostics for STIs has increased significantly over the past 10 years, although adoption of these in low-income and middle-income countries (LMICs) remains limited. Barriers to POC adoption by patients include the cost of tests, the inconvenience of lengthy clinic visits, low perceived risk, stigma, lack of partner notification, and lack of trust in healthcare providers. Lowering the cost of true POC lateral flow devices, interfacing these with digital or eHealth technologies, and enabling self-testing/self-sampling will overcome some of these barriers in LMICs. Ensuring linkage of diagnostic tests to subsequent care remains one of the major concerns about self-testing, irrespective of geography, although available evidence from HIV self-testing suggests that linkage to care is similar to that for facility-based testing.

SUMMARY

Increasing access to sensitive STI true POC tests will strengthen reproductive healthcare in LMICs. Although HIV self-testing is demonstrably useful in LMICs, there is an urgent need for randomized trials evaluating the utility and cost-effectiveness of similar tests for other sexually transmitted infections.

Improved rapid diagnostic tests to detect syphilis and yaws: a systematic review and meta-analysis

BACKGROUND

Current rapid tests for syphilis and yaws can detect treponemal and non-treponemal antibodies. We aimed to critically appraise the literature for rapid diagnostic tests (RDTs) which can better distinguish an active infection of syphilis or yaws.

METHODS

We conducted a systematic review and meta-analysis, searching five databases between January 2010 and October 2021 (with an update in July 2022). A generalised linear mixed model was used to conduct a bivariate meta-analysis for the pooled sensitivity and specificity. Heterogeneity was assessed using the I2 statistic. We used the Quality Assessment of Diagnostic Accuracy Studies (QUADAS) to assess the risk of bias and Grading of Recommendations, Assessment, Development and Evaluations (GRADE) to evaluate the certainty of evidence.

RESULTS

We included 17 studies for meta-analyses. For syphilis, the pooled sensitivity and specificity of the treponemal component were 0.93 (95% CI: 0.86 to 0.97) and 0.98 (95% CI: 0.96 to 0.99), respectively. For the non-treponemal component, the pooled sensitivity and specificity were 0.90 (95% CI: 0.82 to 0.95) and 0.97 (95% CI: 0.92 to 0.99), respectively. For yaws, the pooled sensitivity and specificity of the treponemal component were 0.86 (95% CI: 0.66 to 0.95) and 0.97 (95% CI: 0.94 to 0.99), respectively. For the non-treponemal component, the pooled sensitivity and specificity were 0.80 (95% CI: 0.55 to 0.93) and 0.96 (95% CI: 0.92 to 0.98), respectively.

CONCLUSIONS

RDTs that can differentiate between active and previously treated infections could optimise management by providing same-day treatment and reducing unnecessary treatment.

PROSPERO REGISTRATION NUMBER

CRD42021279587.