An Evaluation of the Relative Sensitivities of the Venereal Disease Research Laboratory Test and the Treponema pallidum Particle Agglutination Test Among Patients Diagnosed With Primary Syphilis

CDC Laboratory Recommendations for Syphilis Testing, United States, 2024

This report provides new CDC recommendations for tests that can support a diagnosis of syphilis, including serologic testing and methods for the identification of the causative agent Treponema pallidum. These comprehensive recommendations are the first published by CDC on laboratory testing for syphilis, which has traditionally been based on serologic algorithms to detect a humoral immune response to T. pallidum. These tests can be divided into nontreponemal and treponemal tests depending on whether they detect antibodies that are broadly reactive to lipoidal antigens shared by both host and T. pallidum or antibodies specific to T. pallidum, respectively. Both types of tests must be used in conjunction to help distinguish between an untreated infection or a past infection that has been successfully treated. Newer serologic tests allow for laboratory automation but must be used in an algorithm, which also can involve older manual serologic tests. Direct detection of T. pallidum continues to evolve from microscopic examination of material from lesions for visualization of T. pallidum to molecular detection of the organism. Limited point-of-care tests for syphilis are available in the United States; increased availability of point-of-care tests that are sensitive and specific could facilitate expansion of screening programs and reduce the time from test result to treatment. These recommendations are intended for use by clinical laboratory directors, laboratory staff, clinicians, and disease control personnel who must choose among the multiple available testing methods, establish standard operating procedures for collecting and processing specimens, interpret test results for laboratory reporting, and counsel and treat patients. Future revisions to these recommendations will be based on new research or technologic advancements for syphilis clinical laboratory science.

Evaluation of a minimal array of Treponema pallidum antigens as biomarkers for syphilis diagnosis, infection staging, and response to treatment

IMPORTANCE

This manuscript explores the host humoral response to selected antigens of the syphilis agent during infection to evaluate their potential use as diagnostic tests and markers for treatment.

Molecular Characterization of Genital and Extragenital Lesions With the PlexPCR VHS Assay in Patients Diagnosed With Syphilis

Background

Syphilis diagnosis relies on immunologic markers and clinical protocols. However, syphilitic lesions can be confused with other genital ulcer diseases.

Methods

Using a PlexPCR VHS assay, we analyzed lesion DNA samples from 87 individuals who were clinically diagnosed with early syphilis infection and had at least 1 positive serologic test result. DNA was detected by the PlexPCR VHS multiplex assay and β-globin genes.

Results

Among the participants, 99% (86/87) had a positive rapid treponemal test result. DNA was successfully detected in 91% (79/87) of the lesion samples. PlexPCR VHS identified 5 herpes simplex virus (HSV)/Treponema pallidum coinfections (2 HSV-1 and 3 HSV-2), only T pallidum DNA in 62% (49/79), and only HSV-2 in 12.7% (10/79). While 19% (15/79) were negative for all pathogens, none were varicella zoster virus positive. The PlexPCR VHS had 68.4% agreement with the clinical diagnosis.

Conclusions

Since the PlexPCR VHS detects multiple organisms simultaneously, it can help to confirm actual syphilis and identify other pathogen coinfections or the pathogen causing the ulcer.

A comprehensive review for machine learning based human papillomavirus detection in forensic identification with multiple medical samples

Human papillomavirus (HPV) is a sexually transmitted virus. Cervical cancer is one of the highest incidences of cancer, almost all patients are accompanied by HPV infection. In addition, the occurrence of a variety of cancers is also associated with HPV infection. HPV vaccination has gained widespread popularity in recent years with the increase in public health awareness. In this context, HPV testing not only needs to be sensitive and specific but also needs to trace the source of HPV infection. Through machine learning and deep learning, information from medical examinations can be used more effectively. In this review, we discuss recent advances in HPV testing in combination with machine learning and deep learning.

Evaluation of the AIX1000 Automated Rapid Plasma Reagin Assay in a High-Prevalence Setting

BACKGROUND

Manually performed nontreponemal assays, such as rapid plasma reagin (RPR), are labor intensive and time consuming. Recently, commercial automated RPR assays gained attention. The aim of this study was to compare the qualitative and quantitative performance of the AIX1000 (RPR-A; Gold Standard Diagnostics) to a manual RPR test (RPR-M; Becton Dickinson Macrovue) within a high-prevalence setting.

METHODS

A retrospective panel of 223 samples was selected for comparison between RPR-A and RPR-M, including 24 samples from patients with known syphilis stages and 57 samples from 11 patients in follow-up. In addition, 127 samples obtained during routine syphilis diagnosis with RPR-M were analyzed prospectively with AIX1000.

RESULTS

Overall qualitative concordance (percent agreement) between both assays was 92.0% in the retrospective and 89.0% in the prospective panel. Of 32 discordances, 28 were explained by a treated syphilis infection still positive in one assay and already negative in the other. One sample was false positive with RPR-A, 1 infection remained undetected by RPR-M, and 2 remained undetected by RPR-A. A hook effect was apparent on the AIX1000 at RPR-A titers from 1:32 onward; however, no infections were missed. Accepting a ±1 titer difference, quantitative concordance between both assays reached 73.1% and 98.4% for the retrospective and prospective panels, respectively, with an upper limit of reactivity for RPR-A at 1:256.

CONCLUSIONS

The AIX1000 showed a similar performance to Macrovue RPR with the exception of a negative deviation for high-titer samples. Within the reverse algorithm used in our high-prevalence setting, AIX1000's main advantage is automation.

Syphilis

Syphilis is an important public health problem in the U.S. and many high-income nations. The rates of syphilis continue to increase and there is an urgent need for medical providers of a variety of backgrounds to recognize this disease. In this review, we cover the key clinical findings of syphilis and provide an overview of the diagnosis and management of this disease in adults.

Comparison of 17 serological treponemal and nontreponemal assays for syphilis: A retrospective cohort study

Objectives

Rapid plasma reagin (RPR) and Treponema pallidum (TP) antibody test kits are often used to diagnose syphilis, although the relationship between their measured values is unclear. We aimed to reveal the relevance of these kits’ results.

Design and methods

In all, 143 sera from 110 patients were tested using 12 TP kits and 5 RPR kits and the results compared.

Results

The specificity and sensitivity of RPR kits were 81–96% and 95–100%, respectively. The correlation coefficients (0.849–0.934) considerably differed between the manual RPR card test and latex agglutination (LA) assay kits. The following sensitivities were obtained: 82–91% for TP fluorescent treponemal antibody absorption assay (FTA-ABS), TP hemagglutination assay (HA), and TP particle agglutination assay (PA); 94–95% for TP LAs; and 92–100% for chemiluminescent immunoassay (CLIA), chemiluminescent enzyme immunoassay (CLEIA), and immunochromatography assay (IC). Correlation coefficients between TP kits were 0.753–0.974, and the measured values varied. Changes in RPR and quantifiable TP kits were the same for patients with reinfected syphilis and with syphilis under treatment.

Conclusions

RPR tests had lower specificity than TP antibody tests. RPR card test and RPR LAs had similar specificity and sensitivity, but their measured values were different. RPR should be measured using automatic RPR LA without setting the upper limit of the reported value. RPR LA should also be standardized. The sensitivity of TP antibody was better in CLIA, CLEIA, and IC than in FTA-ABS, HA, PA, and LA. Therefore, TP antibody kits should be standardized and quantified.

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RPR CT and four RPR LAs have similar specificity and sensitivity.

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RPR CT and four RPR LAs have different measured values.

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CLIA, CLEIA, and IC have more sensitive TP antibodies than other tests.

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The measured values of 12 TP antibody kits vary.

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Quantitative TP antibodies are similar to RPR in the clinical course of syphilis.

A suite of PCR-LwCas13a assays for detection and genotyping of Treponema pallidum in clinical samples

The performance of commonly used assays for diagnosis of syphilis varies considerably depending on stage of infection and sample type. In response to the need for improved syphilis diagnostics, we develop assays that pair PCR pre-amplification of the tpp47 gene of Treponema pallidum subsp. pallidum with CRISPR-LwCas13a. The PCR-LwCas13a assay achieves an order of magnitude better analytical sensitivity than real-time PCR with equivalent specificity. When applied to a panel of 216 biological specimens, including 135 clinically confirmed primary and secondary syphilis samples, the PCR-LwCas13a assay demonstrates 93.3% clinical sensitivity and 100% specificity, outperforming tpp47 real-time PCR and rabbit-infectivity testing. We further adapt this approach to distinguish Treponema pallidum subsp. pallidum lineages and identify genetic markers of macrolide resistance. Our study demonstrates the potential of CRISPR-based approaches to improve diagnosis and epidemiological surveillance of syphilis.

Diagnostic Accuracy of Rapid Point-of-Care Tests for Detecting Active Syphilis: A Systematic Review and Meta-Analysis

BACKGROUND

Syphilis represents an important cause of morbidity and mortality. Point-of-care (POC) test offers the advantages of diagnosing the condition and the possibility of starting treatment immediately.

METHODS

MEDLINE, Embase, CENTRAL, LILACS, World Health Organization International Clinical Trials Registry Platform, Web of Science, OpenGrey, and DARE were searched without language restrictions from inception to September 30, 2020. Diagnostic test accuracy studies that enrolled men and nonpregnant women of reproductive age under field conditions were analyzed. Only studies wherein all the patients had undergone a rapid POC test and those that included the reference standard (treponemal plus nontreponemal test) were eligible for inclusion. Studies were independently assessed for inclusion, data extraction, and bias risk. The data from these studies were extracted for meta-analyses. The quality of the evidence was assessed using the GRADE approach. Registration Prospero CRD42018107532.

RESULTS

Nine studies with 9666 participants were included. Nine POC brands were assessed. Sensitivities of the tests ranged from 0.67 to 1.00 and specificities from 0.93 to 1.00. The mean sensitivity and specificity of all the included studies was 0.86 (95% confidence interval, 0.79-0.91) and 0.98 (95% confidence interval, 0.96-0.99), respectively.

CONCLUSIONS

Based on the results of this systematic review, the POC test for syphilis showed good sensitivity and excellent specificity.

Analytical Performance Characteristics of a New Transcription-Mediated Amplification Assay for Treponema pallidum

This study evaluated the performance characteristics of a new research-use-only transcription-mediated amplification (TMA) assay for the detection of rRNA from Treponema pallidum. Analytical sensitivity determined using dark-field microscopy-quantitated T. pallidum was 1.4 organisms/ml (95% confidence interval [CI], 0.7 to 6.33 organisms/ml). Dilution of in vitro-transcribed (IVT) T. pallidum RNA in Aptima sample transport medium (STM) yielded 100% positivity (n = 3) at 10 copies/ml (4 copies/reaction). Analytical specificity testing of nontarget microorganisms (n = 59), including the closely related nonsyphilis treponemes Treponema denticola and Treponema phagedenis, yielded 0% positivity. TMA testing of mucosal swab specimens collected from men who have sex with men (MSM) attending a sexually transmitted disease clinic yielded 1.8% (17/944) positive results. A collection of 56 serum specimens obtained from a separate cohort of patients with known rapid plasma reagin (RPR) statuses and clinical diagnoses of syphilis was 19.6% (11/56) TMA positive overall and 29.7% (11/37) positive among subjects with syphilis diagnoses, including 8 (36.3%) of 22 persons with primary or secondary syphilis, 2 (20%) of 10 persons with early latent syphilis, and 1 (20%) of 5 persons with late latent or unstaged syphilis. None (0%) of the 18 RPR-positive sera from patients with histories of treated syphilis were TMA positive. These results show that TMA is an analytically sensitive and specific method for the detection of T. pallidum rRNA and is compatible with serum specimens in addition to pharyngeal and rectal mucocutaneous swab specimens. Automated real-time TMA testing for T. pallidum may be useful as an adjunctive method with serology for screening and diagnostic testing of selected patient populations for syphilis.

Analytical Performance Characteristics of a New Transcription-Mediated Amplification Assay for Treponema pallidum

This study evaluated the performance characteristics of a new research-use-only transcription-mediated amplification (TMA) assay for the detection of rRNA from Treponema pallidum. Analytical sensitivity determined using dark-field microscopy-quantitated T. pallidum was 1.4 organisms/ml (95% confidence interval [CI], 0.7 to 6.33 organisms/ml). Dilution of in vitro-transcribed (IVT) T. pallidum RNA in Aptima sample transport medium (STM) yielded 100% positivity (n = 3) at 10 copies/ml (4 copies/reaction). Analytical specificity testing of nontarget microorganisms (n = 59), including the closely related nonsyphilis treponemes Treponema denticola and Treponema phagedenis, yielded 0% positivity. TMA testing of mucosal swab specimens collected from men who have sex with men (MSM) attending a sexually transmitted disease clinic yielded 1.8% (17/944) positive results. A collection of 56 serum specimens obtained from a separate cohort of patients with known rapid plasma reagin (RPR) statuses and clinical diagnoses of syphilis was 19.6% (11/56) TMA positive overall and 29.7% (11/37) positive among subjects with syphilis diagnoses, including 8 (36.3%) of 22 persons with primary or secondary syphilis, 2 (20%) of 10 persons with early latent syphilis, and 1 (20%) of 5 persons with late latent or unstaged syphilis. None (0%) of the 18 RPR-positive sera from patients with histories of treated syphilis were TMA positive. These results show that TMA is an analytically sensitive and specific method for the detection of T. pallidum rRNA and is compatible with serum specimens in addition to pharyngeal and rectal mucocutaneous swab specimens. Automated real-time TMA testing for T. pallidum may be useful as an adjunctive method with serology for screening and diagnostic testing of selected patient populations for syphilis.

Sensitivity and Specificity of Treponemal-specific Tests for the Diagnosis of Syphilis

We conducted a systematic review of relevant syphilis diagnostic literature to address the question, “What is the sensitivity and specificity of the treponemal tests currently approved by the Food and Drug Administration (FDA) for the diagnosis of syphilis (by stage)?” There were 16 treponemal assays evaluated: 13 immunoassays and 3 manual assays (fluorescent treponemal antibody absorbed test [FTA-ABS], microhemagglutination assay for Treponema pallidum antibodies [MHA-TP], Treponema pallidum particle agglutination assay [TP-PA]). MHA-TP and FTA-ABS were less sensitive in primary and secondary syphilis than TP-PA; TP-PA is the most specific manual treponemal assay. There is insufficient evidence to recommend one particular treponemal immunoassay (eg, enzyme immunoassays, chemiluminescence immunoassays, microbead immunoassays) over another based on published performance data. For diagnosis of neurosyphilis, cerebrospinal fluid (CSF) TP-PA has similar performance to CSF FTA-ABS in studies with patients with definitive or presumptive neurosyphilis. However, CSF treponemal testing has limitations in its sensitivity and specificity and should be interpreted within the context of the clinical scenario, additional CSF test results and syphilis prevalence.

Molecular and Direct Detection Tests for Treponema pallidum Subspecies pallidum: A Review of the Literature, 1964-2017

Direct detection methods for Treponema pallidum include dark-field microscopy (DFM), direct fluorescence antibody (DFA) testing, immunohistochemistry (IHC), and nucleic acid amplification tests (NAATs). Here, we reviewed the relevant syphilis diagnostic literature to address 2 main questions with respect to T. pallidum direct detection techniques: “What are the performance characteristics for each direct detection test for T. pallidum and what are the optimal specimen types for each test?” and “What options are available for T. pallidum molecular epidemiology?” To answer these questions, we searched 5 electronic databases (OVID Medline, OVID Embase, CINAHL, Cochrane Library, and Scopus) from 1964 to 2017 using relevant search terms and identified 1928 articles, of which 37 met our inclusion criteria. DFM and DFA sensitivities ranged from 73% to 100% in cases of primary syphilis; and while sensitivity using silver stain histopathology for T. pallidum was generally low (0%–41%), higher performance characteristics were observed for T. pallidum–specific IHC (49–92%). Different genes have been targeted by T. pallidum–specific NAATs, with the majority of studies indicating that sensitivity is primarily dependent on the type of collected biological sample, with highest sensitivity observed in primary lesion exudate (75–95%). Given the rising incidence of syphilis, the development of direct, Food and Drug Administration–cleared T. pallidum NAATs should be considered an immediate priority.

The Traditional or Reverse Algorithm for Diagnosis of Syphilis: Pros and Cons

We reviewed relevant syphilis diagnostic literature to address the question “What diagnostic considerations should be taken into account when screening for syphilis using the traditional or reverse algorithm?” Improved laboratory diagnosis of syphilis is an important element of the effort to reduce syphilis rates. Screening for syphilis is performed using either a nontreponemal or treponemal test (part of the traditional or reverse algorithm, respectively). Both syphilis algorithms are used by laboratories. However, there are limited data on the performance and cost-effectiveness of the algorithms. An expert panel generated “key questions” in the laboratory diagnosis of syphilis. This paper pertains to the key factors that should be considered when deciding whether to screen for syphilis using either the traditional or the reverse algorithm. A systematic literature review was performed, and tables of evidence were created to address this question.

Syphilis Laboratory Guidelines: Performance Characteristics of Nontreponemal Antibody Tests

We reviewed the relevant syphilis diagnostic literature to address the following question: what are the performance characteristics, stratified by the stage of syphilis, for nontreponemal serologic tests? The database search included key terms related to syphilis and nontreponemal tests from 1960–2017, and for data related to the venereal disease research laboratory test from 1940–1960. Based on this review, we report the sensitivity and specificity for each stage of syphilis (primary, secondary, early latent, late latent, or unknown duration; tertiary as well as neurosyphilis, ocular syphilis, and otic syphilis). We also report on reactive nontreponemal tests in conditions other than syphilis, false negatives, and automated nontreponemal tests. Overall, many studies were limited by their sample size, lack of clearly documented clinical staging, and lack of well-defined gold standards. There is a need to better define the performance characteristics of nontreponemal tests, particularly in the late stages of syphilis, with clinically well-characterized samples. Published data are needed on automated nontreponemal tests. Evidence-based guidelines are needed for optimal prozone titrations. Finally, improved criteria and diagnostics for neurosyphilis (as well as ocular and otic syphilis) are needed.

Performance of Treponemal Tests for the Diagnosis of Syphilis

BACKGROUND

Treponemal immunoassays are increasingly used for syphilis screening with the reverse sequence algorithm. There are few data describing performance of treponemal immunoassays compared to traditional treponemal tests in patients with and without syphilis.

METHODS

We calculated sensitivity and specificity of 7 treponemal assays: (1) ADVIA Centaur (chemiluminescence immunoassay [CIA]); (2) Bioplex 2200 (microbead immunoassay); (3) fluorescent treponemal antibody absorption test (FTA-ABS); (4) INNO-LIA (line immunoassay); (5) LIAISON CIA; (6) Treponema pallidum particle agglutination assay (TPPA); and (7) Trep-Sure (enzyme immunoassay [EIA]), using a reference standard combining clinical diagnosis and serology results. Sera were collected between May 2012-January 2013. Cases were characterized as: (1) current clinical diagnosis of syphilis: primary, secondary, early latent, late latent; (2) prior treated syphilis only; (3) no evidence of current syphilis, no prior history of syphilis, and at least 4 of 7 treponemal tests negative.

RESULTS

Among 959 participants, 262 had current syphilis, 294 had prior syphilis, and 403 did not have syphilis. FTA-ABS was less sensitive for primary syphilis (78.2%) than the immunoassays or TPPA (94.5%-96.4%) (all P ≤ .01). All immunoassays were 100% sensitive for secondary syphilis, 95.2%-100% sensitive for early latent disease, and 86.8%-98.5% sensitive in late latent disease. TPPA had 100% specificity.

CONCLUSIONS

Treponemal immunoassays demonstrated excellent sensitivity for secondary, early latent, and seropositive primary syphilis. Sensitivity of FTA-ABS in primary syphilis was poor. Given its high specificity and superior sensitivity, TPPA is preferred to adjudicate discordant results with the reverse sequence algorithm over the FTA-ABS.

Centers for Disease Control and Prevention Syphilis Summit-Diagnostics and Laboratory Issues

Syphilis, caused by the bacterium Treponema pallidum, is on the rise in the United States particularly among men who have sex with men. The disease is complex with varied clinical manifestations and challenges remain in the laboratory diagnostic setting because T. pallidum is noncultivable and no single test can accurately diagnose all stages of the disease. There are missed opportunities for the use of direct detection tests in primary and secondary syphilis. The increasing use of different reverse sequence algorithms for serology testing without validation in populations with varying risks for syphilis makes the interpretation of test results difficult; this has led to concerns about diagnostic errors or overtreatment. On the other hand, the traditional algorithm may miss some early primary syphilis cases, which is of concern in high-risk populations. The potential utility of rapid syphilis serology tests in different settings or populations remains to be determined. The implementation of better tests and appropriate testing algorithms together with laboratory guidelines for test use in general will lead to better diagnostic options for syphilis.

Treponema pallidum Nucleic Acid Amplification Testing To Augment Syphilis Screening among Men Who Have Sex with Men

Syphilis rates in much of the world are now at their highest levels in almost three decades, and new approaches to controlling syphilis, including diagnostic tests with shorter window periods, are urgently needed. We compared the sensitivity of syphilis serological testing using the rapid plasma reagin (RPR) test with that of the combination of serological testing and an experimental 23S rRNA Treponema pallidum real-time transcription-mediated amplification (TMA) assay performed on rectal and pharyngeal mucosal swabs. T. pallidum PCR assays for the tpp47 gene were performed on all TMA-positive specimens, as well as specimens from 20 randomly selected TMA-negative men. A total of 545 men who have sex with men (MSM) who were seen in a sexually transmitted disease clinic provided 506 pharyngeal specimens and 410 rectal specimens with valid TMA results. Twenty-two men (4%) were diagnosed with syphilis on the basis of positive RPR test results and clinical diagnoses, including 3 men with primary infections, 8 with secondary syphilis, 9 with early latent syphilis, 1 with late latent syphilis, and 1 with an unstaged infection. Two additional men were diagnosed based on positive rectal mucosal TMA assay results alone, and both also tested positive by PCR assay. At least 1 specimen was TMA positive for 12 of 24 men with syphilis (sensitivity, 50% [95% confidence interval [CI], 29 to 71%]). RPR testing and clinical diagnosis were 92% sensitive (95% CI, 73 to 99%) in identifying infected men. Combining mucosal TMA testing and serological testing may increase the sensitivity of syphilis screening in high-risk populations.

Sexually transmitted infections - laboratory diagnosis

The Guidelines Project, an initiative of the Brazilian Medical Association, aims to combine information from the medical field in order to standardize producers to assist the reasoning and decision-making of doctors. The information provided through this project must be assessed and criticized by the physician responsible for the conduct that will be adopted, depending on the conditions and the clinical status of each patient.

Screening for Sexually Transmitted Diseases

This article discusses sexually transmitted infections (STI) screening and focuses on reportable STIs. This includes gonorrhea, chlamydia, syphilis, and human immunodeficiency virus. Hepatitis B and C, trichomonas, and herpes are covered as well. Recommendations are summarized from the various organizations that produce screening recommendations. These screening recommendations only apply to asymptomatic individuals. Once an individual has symptoms, testing becomes diagnostic. It is important to know the prevalence of STIs within your population. If you work in a population with a high prevalence of a specific disease, you may want to screen regardless of the recommendations.

Sexually Transmitted Infections in Pregnant Women: Integrating Screening and Treatment into Prenatal Care

Chlamydia, gonorrhea, and syphilis continue to be significant burdens to the health of pregnant women and their children despite easy and effective guidance for screening and treatment. Specific guidelines exist for screening for these infections as well as treatment and follow-up. In this article, we review the epidemiology of chlamydia, gonorrhea, and syphilis. Testing methodology is also reviewed as molecular-based techniques have replaced culture as the current gold standard tests of choice for chlamydia and gonorrhea. The nontreponemal and treponemal serologic diagnostic and screening approach to syphilis has undergone less change. Treatment for gonorrhea includes a one-time dose of parenteral ceftriaxone and oral azithromycin. This treatment regimen not only addresses the possible gonococcal resistance seen in recent years but also treats chlamydia, which may present similarly or co-infect the same patient. Syphilis treatment in both pregnant women and their infected neonates remains with penicillin G formulations. It is crucial to establish close follow-up evaluation for the pregnant woman infected with these sexually transmitted infections to ensure adequate treatment and help prevent perinatal spread of the infection.

Using Treponemal Assay Signal Strength Cutoff Ratios To Predict Syphilis Infection

Syphilis screening with the reverse algorithm, a treponemal test for screening followed by a nontreponemal test if reactive, is increasingly being used. That algorithm has several advantages, including use of an automated screening test, saving on laboratory time and costs, as well as detection of very early syphilis infection. However, under that algorithm, in situations where the treponemal result is positive and the nontreponemal result is nonreactive a second treponemal test must be performed, which may actually lead to inefficiencies in the laboratory. In this issue of the Journal of Clinical Microbiology, Y. F. Fakile et al. (J Clin Microbiol 56:e01165-17, 2017, https://doi.org/10.1128/JCM.01165-17) report the results of their study, which demonstrates the capability of signal strength ratio cutoffs for automated treponemal immunoassays to predict the outcome of repeat treponemal testing. Their findings suggest that anti-treponemal signal strength ratio values above a cutoff value can be used in lieu of repeat treponemal tests.

Syphilis

Treponema pallidum subspecies pallidum (T. pallidum) causes syphilis via sexual exposure or via vertical transmission during pregnancy. T. pallidum is renowned for its invasiveness and immune-evasiveness; its clinical manifestations result from local inflammatory responses to replicating spirochaetes and often imitate those of other diseases. The spirochaete has a long latent period during which individuals have no signs or symptoms but can remain infectious. Despite the availability of simple diagnostic tests and the effectiveness of treatment with a single dose of long-acting penicillin, syphilis is re-emerging as a global public health problem, particularly among men who have sex with men (MSM) in high-income and middle-income countries. Syphilis also causes several hundred thousand stillbirths and neonatal deaths every year in developing nations. Although several low-income countries have achieved WHO targets for the elimination of congenital syphilis, an alarming increase in the prevalence of syphilis in HIV-infected MSM serves as a strong reminder of the tenacity of T. pallidum as a pathogen. Strong advocacy and community involvement are needed to ensure that syphilis is given a high priority on the global health agenda. More investment is needed in research on the interaction between HIV and syphilis in MSM as well as into improved diagnostics, a better test of cure, intensified public health measures and, ultimately, a vaccine.

Global challenges in human immunodeficiency virus and syphilis coinfection among men who have sex with men

INTRODUCTION

Syphilis and human immunodeficiency virus (HIV) coinfection disproportionately affects men who have sex with men (MSM), and the rate of coinfection has been increasing over the last decade. HIV and syphilis coinfection is particularly challenging because the infections interact synergistically thereby increasing the risk of acquisition and transmission as well as accelerating disease progression. Areas covered: This paper reviews and summarizes the epidemiology, pathogenesis, diagnosis, clinical management and prevention of HIV and syphilis coinfection among MSM. Expert commentary: Research does not support a different syphilis treatment for coinfected individuals; however, coinfection may warrant a recommendation for antiretroviral therapy. In order to reverse the epidemic of syphilis and HIV coinfection, there needs to be greater awareness, improved cultural sensitivity among health care providers, improved access to preventative services and increased screening for syphilis and HIV.

State of the art syphilis diagnostics: rapid point-of-care tests

Syphilis remains an important and entirely preventable cause of stillbirth and neonatal mortality. More than 1 million women with active syphilis become pregnant each year. Without treatment, 25% of them will deliver a stillborn baby, 33% will deliver a live low-birth weight baby with an increased chance of dying in the first month of life. Adverse pregnancy outcomes due to syphilis can be prevented by screening pregnant women, and treating those who test positive with a single dose of penicillin before 28 weeks gestation. Until recently access to screening in low- and middle-income countries has been limited, since screening tests have been laboratory based, requiring equipment, electricity and trained laboratory staff. Now a number of rapid, cheap, simple and accurate screening tests are available and can give a result in 15-20 min, enabling those who require treatment to be treated at their first visit.

Characterizing the syphilis epidemic among men who have sex with men in Lima, Peru to identify new treatment and control strategies

BACKGROUND

Syphilis is an important sexually transmitted infection (STI) with serious public health consequences. Among men who have sex with men (MSM) in Lima, the prevalence and incidence are extraordinarily high. Current syndromic approaches, however, fail to identify asymptomatic cases, and in settings where large proportions of individuals test positive again after treatment, it is frequently difficult to distinguish treatment failure from re-infection. Thus, new approaches are needed to improve treatment strategies and public health control efforts.

METHODS/DESIGN

Study participants will undergo baseline testing for syphilis infection along with a behavioral survey covering demographics, sexual behavior, drug and alcohol abuse and health-care seeking behavior. The cohort will be followed for 18 months at three-month intervals. Blood and earlobe scrapings will also be collected for T. pallidum DNA testing, to create molecular markers for subtyping. We will also perform cytokine testing on collected samples in order to create host immunologic profiles associated with recurrence, re-infection, treatment failure and success.

DISCUSSION

Advances in social epidemiology, molecular typing and characterization of host immune responses will offer promise in developing new understandings of syphilis management. We will share our findings with the Peruvian Ministry of Health and other public health organizations, to identify new approaches of case detection and successful treatment.

Usefulness of IgM-specific enzyme immunoassays for serodiagnosis of syphilis: comparative evaluation of three different assays

OBJECTIVES

IgM antibodies are usually the first to be produced during treponemal infection. Three commercially available enzyme immunoassays (EIA) for detection of IgM antibodies against Treponema pallidum were evaluated.

METHODS

Results of the Anti-Treponema-pallidum-ELISA (IgM; Euroimmun), Pathozyme Syphilis M Capture (Omega Diagnostics) and recomWell Treponema IgM (Mikrogen) were compared with those of the T. pallidum particle agglutination (TPPA) and the Venereal Disease Research Laboratory (VDRL) tests for 307 serum samples.

RESULTS

The overall sensitivity (95% confidence interval [CI]) of the TPPA was 100% (97.7-100%) compared to 83.3% (76.5-88.8%) of the VDRL, 88.5% (82.4-93.0%) of the Pathozyme, 84.6% (78.0-89.9) of the Euroimmun, and 73.6% (66.1-80.4%) of a modified recomWell test procedure. Specificities were in the range of 91.4-100%. In primary syphilis, sensitivities of the Pathozyme (89.8%; 95% CI, 79.2-96.2%) and Euroimmun tests (81.4%; 95% CI, 69.1-90.3%) were significantly higher (p < 0.05) than the sensitivity of the VDRL test (61%; 95% CI, 47.4-73.5%). IgM EIAs even were positive in some cases of suspected very early infection where the VDRL was non-reactive and the TPPA was indeterminate.

CONCLUSIONS

In cases of suspected early infection specific IgM EIAs should be used in addition to other screening tests. The VDRL is not recommended for screening.

Are Treponema pallidum specific rapid and point-of-care tests for syphilis accurate enough for screening in resource limited settings? Evidence from a meta-analysis

BACKGROUND

Rapid and point-of-care (POC) tests for syphilis are an invaluable screening tool, yet inadequate evaluation of their diagnostic accuracy against best reference standards limits their widespread global uptake. To fill this gap, a systematic review and meta-analysis was conducted to evaluate the sensitivity and specificity of rapid and POC tests in blood and serum samples against Treponema pallidum (TP) specific reference standards.

METHODS

Five electronic databases (1980-2012) were searched, data was extracted from 33 articles, and Bayesian hierarchical models were fit.

RESULTS

In serum samples, against a TP specific reference standard point estimates with 95% credible intervals (CrI) for the sensitivities of popular tests were: i) Determine, 90.04% (80.45, 95.21), ii) SD Bioline, 87.06% (75.67, 94.50), iii) VisiTect, 85.13% (72.83, 92.57), and iv) Syphicheck, 74.48% (56.85, 88.44), while specificities were: i) Syphicheck, 99.14% (96.37, 100), ii) Visitect, 96.45% (91.92, 99.29), iii) SD Bioline, 95.85% (89.89, 99.53), and iv) Determine, 94.15% (89.26, 97.66). In whole blood samples, sensitivities were: i) Determine, 86.32% (77.26, 91.70), ii) SD Bioline, 84.50% (78.81, 92.61), iii) Syphicheck, 74.47% (63.94, 82.13), and iv) VisiTect, 74.26% (53.62, 83.68), while specificities were: i) Syphicheck, 99.58% (98.91, 99.96), ii) VisiTect, 99.43% (98.22, 99.98), iii) SD Bioline, 97.95%(92.54, 99.33), and iv) Determine, 95.85% (92.42, 97.74).

CONCLUSIONS

Rapid and POC treponemal tests reported sensitivity and specificity estimates comparable to laboratory-based treponemal tests. In resource limited settings, where access to screening is limited and where risk of patients lost to follow up is high, the introduction of these tests has already been shown to improve access to screening and treatment to prevent stillbirths and neonatal mortality due to congenital syphilis. Based on the evidence, it is concluded that rapid and POC tests are useful in resource limited settings with poor access to laboratories or screening for syphilis.

Serological response to treatment of syphilis according to disease stage and HIV status

The serological response to treatment was studied in 264 syphilis patients; it was influenced by syphilis stage but not by human immunodeficiency virus infection and reinfection. Some of the recommendations of current guidelines are critically discussed, and amendments are proposed.

Background. Serology is the mainstay for syphilis diagnosis and treatment monitoring. We investigated serological response to treatment of syphilis according to disease stage and HIV status.

Methods. A retrospective cohort study of 264 patients with syphilis was conducted, including 90 primary, 133 secondary, 33 latent, and 8 tertiary syphilis cases. Response to treatment as measured by the Venereal Disease Research Laboratory (VDRL) test and a specific IgM (immunoglobulin M) capture enzyme-linked immunosorbent assay (ELISA; Pathozyme-IgM) was assessed by Cox regression analysis.

Results. Forty-two percent of primary syphilis patients had a negative VDRL test at their diagnosis. Three months after treatment, 85%–100% of primary syphilis patients had reached the VDRL endpoint, compared with 76%–89% of patients with secondary syphilis and 44%–79% with latent syphilis. In the overall multivariate Cox regression analysis, serological response to treatment was not influenced by human immunodeficiency virus (HIV) infection and reinfection. However, within primary syphilis, HIV patients with a CD4 count of <500 cells/μL had a slower treatment response (P = .012). Compared with primary syphilis, secondary and latent syphilis showed a slower serological response of VDRL (P = .092 and P < .001) and Pathozyme-IgM tests (P < .001 and P = .012).

Conclusions. The VDRL should not be recommended as a screening test owing to lack of sensitivity. The syphilis disease stage significantly influences treatment response whereas HIV coinfection only within primary syphilis has an impact. VDRL test titers should decline at least 4-fold within 3–6 months after therapy for primary or secondary syphilis, and within 12–24 months for latent syphilis. IgM ELISA might be a supplement for diagnosis and treatment monitoring.

Results of a 25-year longitudinal analysis of the serologic incidence of syphilis in a cohort of HIV-infected patients with unrestricted access to care

BACKGROUND

The well-described biologic and epidemiologic associations of syphilis and HIV are particularly relevant to the military, as service members are young and at risk for sexually transmitted infections. We therefore used the results of serial serologic testing to determine the prevalence, incidence, and risk factors for incident syphilis in a cohort of HIV-infected Department of Defense beneficiaries.

METHODS

Participants with a positive nontreponemal test at HIV diagnosis that was confirmed on treponemal testing were categorized as prevalent cases, and participants with an initial negative nontreponemal test who subsequently developed a confirmed positive nontreponemal test were categorized as incident cases.

RESULTS

At HIV diagnosis, the prevalence of syphilis was 5.8% (n = 202). A total of 4239 participants contributed 27,192 person-years (PY) to the incidence analysis and 347 (8%) developed syphilis (rate, 1.3/100 PY; [1.1, 1.4]). Syphilis incidence was highest during the calendar years 2006 to 2009 (2.5/100 PY; [2.0, 2.9]). In multivariate analyses, younger age (per 10 year increase hazard ratio [HR], 0.8; [0.8-0.9]), male gender (HR, 5.6; [2.3-13.7]), non-European-American ethnicity (African-American HR, 3.2; [2.5-4.2]; Hispanic HR, 1.9; [1.2-3.0]), and history of hepatitis B (HR, 1.5; [1.2-1.9]) or gonorrhea (HR, 1.4; [1.1-1.8]) were associated with syphilis.

CONCLUSIONS

The significant burden of disease both at and after HIV diagnosis, observed in this cohort, suggests that the cost-effectiveness of extending syphilis screening to at-risk military members should be assessed. In addition, HIV-infected persons continue to acquire syphilis, emphasizing the continued importance of prevention for positive programs.

Evaluation of a PCR test for detection of treponema pallidum in swabs and blood

Syphilis diagnosis is based on clinical observation, serological analysis, and dark-field microscopy (DFM) detection of Treponema pallidum subsp. pallidum, the etiological agent of syphilis, in skin ulcers. We performed a nested PCR (nPCR) assay specifically amplifying the tpp47 gene of T. pallidum from swab and blood specimens. We studied a cohort of 294 patients with suspected syphilis and 35 healthy volunteers. Eighty-seven of the 294 patients had primary syphilis, 103 had secondary syphilis, 40 had latent syphilis, and 64 were found not to have syphilis. The T. pallidum nPCR results for swab specimens were highly concordant with syphilis diagnosis, with a sensitivity of 82% and a specificity of 95%. Reasonable agreement was observed between the results obtained with the nPCR and DFM methods (kappa = 0.53). No agreement was found between the nPCR detection of T. pallidum in blood and the diagnosis of syphilis, with sensitivities of 29, 18, 14.7, and 24% and specificities of 96, 92, 93, and 97% for peripheral blood mononuclear cell (PBMC), plasma, serum, and whole-blood fractions, respectively. HIV status did not affect the frequency of T. pallidum detection in any of the specimens tested. Swab specimens from mucosal or skin lesions seemed to be more useful than blood for the efficient detection of the T. pallidum genome and, thus, for the diagnosis of syphilis.

Evaluation of a fully automated treponemal test and comparison with conventional VDRL and FTA-ABS tests

We evaluated analytic performances of an automated treponemal test and compared this test with the Venereal Disease Research Laboratory test (VDRL) and fluorescent treponemal antibody absorption test (FTA-ABS). Precision performance of the Architect Syphilis TP assay (TP; Abbott Japan, Tokyo, Japan) was assessed, and 150 serum samples were assayed with the TP before and after heat inactivation to estimate the effect of heat inactivation. A total of 616 specimens were tested with the FTA-ABS and TP, and 400 were examined with the VDRL. The TP showed good precision performance with total imprecision of less than a 10% coefficient of variation. An excellent linear relationship between results before and after heat inactivation was observed (R(2) = 0.9961). The FTA-ABS and TP agreed well with a κ coefficient of 0.981. The concordance rate between the FTA-ABS and TP was the highest (99.0%), followed by the rates between FTA-ABS and VDRL (85.0%) and between TP and VDRL (83.8%). The automated TP assay may be adequate for screening for syphilis in a large volume of samples and can be an alternative to FTA-ABS.

Screening for syphilis with the treponemal immunoassay: analysis of discordant serology results and implications for clinical management

BACKGROUND

Screening for syphilis with treponemal chemiluminescence immunoassays (CIA) identifies patients with discordant serology who are not identified with traditional screening methods (eg, CIA-positive, rapid plasma regain (RPR)-negative). We sought to describe the clinical characteristics and management of patients with discordant syphilis serology.

METHODS

From August 2007-October 2007, patients with CIA-positive, RPR-negative serology were tested with the Treponema pallidum particle agglutination assay (TP-PA) at Kaiser Permanente Northern California. Clinical and demographic characteristics, prior syphilis history and CIA index values were compared for CIA-positive, RPR-negative patients according to TP-PA status.

RESULTS

Of 21,623 assays, 439 (2%) were CIA-positive and 255/439 (58%) were RPR-negative; subsequently, 184 (72%) were TP-PA-positive and 71 (28%) were TP-PA--negative. TP-PA--positive patients were more likely to be male, HIV-positive, homosexual, previously treated for syphilis (57% versus 9%), with higher median CIA index values (9.8 versus 1.6) (all P < .0001). After repeat testing, 7/31 (23%) CIA-positive, RPR-negative, TP-PA--negative patients seroreverted to CIA-negative.

CONCLUSIONS

TP-PA results in conjunction with clinical/behavioral assessment helped guide the management of patients with CIA-positive, RPR-negative serology. TP-PA-positive patients were both highly likely to have prior syphilis and major epidemiologic risk factors for syphilis. CIA-positive, RPR-negative, TP-PA-negative serology may represent a false-positive CIA in low-prevalence populations.

Major directions in the development of diagnostics technologies indermatovenerology

This review describes major directions in the development of laboratory diagnostics of STDs and dermatoses in the Russian Federation. It also discusses strategic directions in the development of diagnostics departments in dermatovenerological institutions (three-level structure of laboratory aid, centralization, automation, standardization of tests, external and internal laboratory quality control, introduction of laboratory information technologies and laboratory information exchange systems). It also substantiates the priority directions in the diagnostics of STDs (etiological diagnostics, acceleration of the cycle of laboratory tests for patients, determination of the resistance of causative agents to antimicrobial drugs, molecular monitoring of the spreading of STDs) and dermatoses (diagnosis verification, diagnosing an organ pathology, marker diagnostics, prevention and prediction of the efficacy and safety of dermatosis treatment).