Laboratory Evaluation of a Commercially Available Rapid Syphilis Test

Treponema Pallidum rapid syphilis compared diagnostic algorithm syphilis in men who have sex with men (MSM)

BACKGROUND

Syphilis infection can be asymptomatic and difficult to diagnose based on clinical symptoms. Early detection and treatment are critical for preventing and controlling syphilis as well as long-term serious complications. A serological examination based on the diagnostic algorithm was used to confirm the diagnosis of syphilis. Syphilis is frequent in high-risk groups, such as men who have sex with men (MSM). Treponema pallidum (TP) rapid can be used for early syphilis detection. The diagnostic value of TP rapid with diagnostic algorithm (RPR-TPHA) utilizing whole blood in MSM should be studied.

OBJECTIVES

To determine the diagnostic value of TP rapid syphilis test compared to a diagnostic algorithm (RPR-TPHA) among MSM.

METHODS

A diagnostic test with a cross-sectional design at Dr Mohammad Hoesin Palembang General Hospital from November 2022 to January 2023. The sampling method was consecutive sampling with a total sample of 83 MSM based on inclusion and exclusion criteria. All samples were tested for RPR, TPHA, and TP rapid. The diagnostic value of TP rapid was evaluated with RPR-TPHA as a diagnostic algorithm for syphilis.

RESULTS

The sensitivity and specificity value of the TP rapid compare diagnostic algorithm as gold standard were 95.8% and 96.6% respectively. Other metrics: positive predictive value (PPV) 92%, negative predictive value (NPV) 98%, positive likelihood ratio (PLR) 28.27, negative likelihood ratio (NLR) 0.04, accuracy 96% and AUC 0.962.

CONCLUSION

The TP rapid test has a high diagnostic value and can be used to establish an early diagnosis of syphilis in MSM.

Syphilis for dermatologists: Current concepts

Dermatologists are familiar with the classic aspects of syphilis. Our objective in this update is to display novel features of sexually acquired syphilis, its pathophysiology, natural history, atypical clinical variants, skin of color, clinical pearls, and prospects. Textbook knowledge, congenital syphilis, epidemiology, and historical data are excluded.

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.

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.

Identifying youth at high risk for sexually transmitted infections in community-based settings using a risk prediction tool: a validation study

BACKGROUND : Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) are the most common bacterial sexually transmitted infections (STIs) worldwide. In the absence of affordable point-of-care STI tests, WHO recommends STI testing based on risk factors. This study aimed to develop a prediction tool with a sensitivity of > 90% and efficiency (defined as the percentage of individuals that are eligible for diagnostic testing) of < 60%.

METHODS

This study offered CT/NG testing as part of a cluster-randomised trial of community-based delivery of sexual and reproductive health services to youth aged 16-24 years in Zimbabwe. All individuals accepting STI testing completed an STI risk factor questionnaire. The outcome was positivity for either CT or NG. Backwards-stepwise logistic regression was performed with p ≥ 0.05 as criteria for exclusion. Coefficients of variables included in the final multivariable model were multiplied by 10 to generate weights for a STI risk prediction tool. A maximum likelihood Receiver Operating Characteristics (ROC) model was fitted, with the continuous variable score divided into 15 categories of equal size. Sensitivity, efficiency and number needed to screen were calculated for different cut-points.

RESULTS

From 3 December 2019 to 5 February 2020, 1007 individuals opted for STI testing, of whom 1003 (99.6%) completed the questionnaire. CT/NG prevalence was 17.5% (95% CI 15.1, 19.8) (n = 175). CT/NG positivity was independently associated with being female, number of lifetime sexual partners, relationship status, HIV status, self-assessed STI risk and past or current pregnancy. The STI risk prediction score including those variables ranged from 2 to 46 with an area under the ROC curve of 0.72 (95% CI 0.68, 0.76). Two cut-points were chosen: (i) 23 for optimised sensitivity (75.9%) and specificity (59.3%) and (ii) 19 to maximise sensitivity (82.4%) while keeping efficiency at < 60% (59.4%).

CONCLUSIONS

The high prevalence of STIs among youth, even in those with no or one reported risk factor, may preclude the use of risk prediction tools for selective STI testing. At a cut-point of 19 one in six young people with STIs would be missed.

A Nurse Case Management HIV Prevention Intervention (Come As You Are) for Youth Experiencing Homelessness: Protocol for a Randomized Wait-list Controlled Trial

Background

Youth experiencing homelessness are more likely than housed youth to experience premature death, suicide, drug overdose, pregnancy, substance use, and mental illness. Yet while youth experiencing homelessness are 6 to 12 times more likely to become infected with HIV than housed youth, with HIV prevalence as high as 16%, many do not access the prevention services they need. Despite adversities, youth experiencing homelessness are interested in health promotion programs, can be recruited and retained in interventions and research studies, and demonstrate improved outcomes when programs are tailored and relevant to them.

Objective

The study aims to compare the efficacy of a nurse case management HIV prevention and care intervention, titled Come As You Are, with that of usual care among youth experiencing homelessness aged 16 to 25 years.

Methods

The study is designed as a 2-armed randomized wait-list controlled trial. Participants (n=450) will be recruited and followed up for 9 months after the intervention for a total study period of 12 months. Come As You Are combines nurse case management with a smartphone-based daily ecological momentary assessment to develop participant-driven HIV prevention behavioral goals that can be monitored in real-time. Youth in the city of Houston, Texas will be recruited from drop-in centers, shelters, street outreach programs, youth-serving organizations, and clinics.

Results

Institutional review board approval (Committee for the Protection of Human Subjects, University of Texas Health Science Center at Houston) was obtained in November 2018. The first participant was enrolled in November 2019. Data collection is ongoing. To date, 123 participants have consented to participate in the study, 89 have been enrolled, and 15 have completed their final follow-up.

Conclusions

There is a paucity of HIV prevention research regarding youth experiencing homelessness. Novel and scalable interventions that address the full continuum of behavioral and biomedical HIV prevention are needed. This study will determine whether a personalized and mobile HIV prevention approach can reduce HIV risk among a hard-to-reach, transient population of youth at high risk.

International Registered Report Identifier (IRRID)

DERR1-10.2196/26716

The laboratory diagnosis of Syphilis

Syphilis is a multisystem infection caused by the spirochaete Treponema pallidum Currently, cases of possible syphilis are commonly investigated using the treponemal serological tests T. pallidum IgG chemiluminescence immunoassay (CLIA) and the T. pallidum particle agglutination (TPPA). The non-treponemal rapid plasma reagin (RPR) flocculation test is used to assess disease activity. There has been a resurgence of syphilis diagnoses in Australia. Large foci of infection have been identified in isolated communities. The remoteness of these locations, in conjunction with the particular socio-cultural characteristics of the population, pose unique challenges to the traditional diagnostic and treatment paradigms for syphilis. As a consequence of this increased incidence of syphilis, there has been interest in the utility of point of care tests (POCT), nucleic acid amplification tests (NAAT), the role of IgM testing in suspected congenital syphilis, and the laboratory investigation of possible neurosyphilis. This review looks at the current status of traditional serological assays and provides an update on more recent methods. It assesses the published literature in this area and makes recommendations for the rational use of pathology testing to aid in the diagnosis of the many facets of syphilis.

Clinical Test Performance of a Rapid Point-of-Care Syphilis Treponemal Antibody Test: A Systematic Review and Meta-analysis

We reviewed relevant syphilis diagnostic literature and conducted a meta-analysis to address the question, "What is the sensitivity and specificity of the Syphilis Health Check, a rapid qualitative test for the detection of human antibodies to Treponema pallidum." The Syphilis Health Check is the only rapid syphilis test currently cleared by the Food and Drug Administration (FDA). We conducted a systematic review and a meta-analysis using Bayesian bivariate random-effects and fixed-effect models to create pooled estimates of sensitivity and specificity of the Syphilis Health Check. We identified 5 test evaluations published in the literature and 10 studies submitted to the FDA and for a Clinical Laboratory Improvement Amendments waiver application. The pooled sensitivity (95% CI) from the laboratory evaluations (n = 5) was 98.5% (92.1-100%), while pooled specificity was 95.9% (81.5-100.0%). The pooled sensitivity for prospective studies (n = 10) was 87.7% ( 71.8-97.2%), while pooled specificity was 96.7% (91.9-99.2%). Using nontreponemal supplemental testing, the sensitivity improved to a pooled sensitivity of 97.0% (94.8-98.6%). The Syphilis Health Check may provide accurate detection of treponemal antibody.

[Rapid diagnosis of sexually transmitted infections : Joint statement of DSTIG, RKI, and PEI, as well as the reference centers for HIV, HBV, and HCV and consulting laboratories for Chlamydia, gonococci, and Treponema pallidum]

In February 2019, the fourth expert meeting on rapid diagnostic tests (RDTs) for sexually transmitted infections (STI) was held at the Robert Koch Institute (RKI) in Berlin. Novel technical developments and new aspects of RDT applications were discussed by representatives from the German STI Society (DSTIG); RKI; the Paul Ehrlich Institute; national reference centers for HIV, HBV, and HCV; and reference laboratories for Chlamydia, gonococci, and Treponema pallidum.As a result of this meeting, we present a revision of the joint statement on STI diagnostics with RDTs from 2017. The Regulation (EU) 2017/746 of the European Parliament and of the Council on in vitro diagnostic medical devices became effective in May 2017 and includes more stringent regulatory requirements for RDTs, mainly concerning conformity of manufacturing processes and performance characteristics of class D in vitro diagnostics (detection of HIV, HBV, HCV, and T. pallidum). Some RDTs for HIV, HCV, and T. pallidum have been evaluated in clinical studies and/or were WHO prequalified and may be used in low-threshold services. Among them are some HIV RDTs available and approved for self-testing. In addition, some HBV RDTs based on detection of HBs antigen (HBsAg) received WHO prequalification. However, false negative results may occur in samples with low HBsAg levels, as for instance in HIV-coinfected patients receiving antiretroviral therapy. For Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG), antigen-based RDTs still do not allow reliable detection of infection. Only PCR-based CT/NG RDTs possess sufficient diagnostic accuracy to be used as point-of-care tests. Rapid PCR tests for NG, however, do not provide any information about antimicrobial resistance.

Evaluation of Rapid Syphilis Testing Using the Syphilis Health Check in Florida, 2015-2016

The Syphilis Health Check (SHC) had low estimated specificity (91.5%) in one Florida county. We investigated use of SHC by a range of Florida publicly-funded programs between 2015 and 2016 to estimate specificity, positive predictive value (PPV), field staff acceptance, and impacts on programmatic outcomes. All reported SHC results were extracted from routinely collected program data. Field staff were surveyed about SHC's utility. Analyses investigated differences between SHC and traditional syphilis testing outcomes. Of 3,630 SHC results reported, 442 were reactive; 92 (20.8%) had prior diagnoses of syphilis; 7 (1.6%) had no further testing. Of the remaining 343; 158 (46.0%) were confirmed cases, 168 (49.0%) were considered false-positive, and 17 (5.0%) were not cases but not clearly false-positive. Estimated specificity of SHC was 95.0%. Overall, 48.5% of positives became confirmed cases (PPV). PPV varied according to prevalence of syphilis in populations tested. Staff (90%) thought SHC helped identify new cases but expressed concern regarding discordance between reactive SHC and lab-based testing. Programmatic outcomes assessment showed shorter time to treatment and increased numbers of partners tested for the SHC group; these enhanced outcomes may better mitigate the spread of syphilis compared to traditional syphilis testing alone, but more research is needed.

Development of a syphilis serum bank to support research, development, and evaluation of syphilis diagnostic tests in the United States

The Centers for Disease Control and Prevention’s (CDC) Division of STD Prevention, in collaboration with the Association of Public Health Laboratories (APHL), is developing a nationally available syphilis serum repository for research of Food and Drug Administration (FDA)-cleared or investigational syphilis diagnostic assays in the United States. State and local public health laboratories (PHL) submitted de-identified residual sera with information on collection date, volume, storage conditions, freeze-thaw cycles, PHL serology results, reported syphilis stage and demographic details if available. Previous test results were blinded and sera (N=152 reported syphilis stage, N = 131 unknown status) were tested at CDC using five FDA-cleared and one investigational syphilis tests. Treponemal and nontreponemal test sensitivity ranged from 76.3–100% and 63.2–100%, respectively, among staged specimens. The conventional treponemal assays showed high concordance of 95.4%. By providing syphilis stage and comprehensive serological test data, developed repository may serve as a valuable resource for diagnostic test validation studies.