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.

Antibody Responses to Two Recombinant Treponemal Antigens (rp17 and TmpA) before and after Azithromycin Treatment for Yaws in Ghana and Papua New Guinea.

WHO and its partners aim to interrupt yaws transmission in countries of endemicity and to certify others as being yaws-free. Transmission can be assessed using rapid plasma reagin (RPR) tests, reflecting current or recent infection, but RPR is operationally impractical. We evaluated changes in antibody levels against two recombinant treponemal antigens, rp17 (also known as Tp17) and TmpA, after antibiotic treatment given as part of a randomized controlled trial for yaws in Ghana and Papua New Guinea. Paired serum samples from children aged 6 to 15 years with confirmed yaws, collected before and after treatment, were tested for antibodies to rp17 and TmpA using a semiquantitative bead-based immunoassay. Of 344 baseline samples, 342 tested positive for anti-rp17 antibodies and 337 tested positive for anti-TmpA antibodies. Six months after treatment, the median decrease in anti-rp17 signal was 3.2%, whereas the median decrease in anti-TmpA was 53.8%. The magnitude of change in the anti-TmpA response increased with increasing RPR titer fold change. These data demonstrate that responses to TmpA decrease markedly within 6 months of treatment whereas (as expected) those to rp17 do not. Incorporating responses to TmpA as a marker of recent infection within an integrated sero-surveillance platform could provide a way to prioritize areas for yaws mapping.

Increased Discrimination of Treponema pallidum Strains by Subtyping With a 4-Component System Incorporating a Mononucleotide Tandem Repeat in rpsA.

A guanine mononucleotide repeat in the rpsA (tp0279) gene was evaluated for improved strain discrimination using 72 Treponema pallidum-positive specimens. The tandem repeat combined with the enhanced Centers for Disease Control and Prevention typing system resulted in increased discrimination and should be useful for molecular epidemiologic studies on syphilis especially in outbreaks and among men who have sex with men.

Field evaluation of two point-of-care tests for syphilis among men who have sex with men, Verona, Italy.

OBJECTIVES: The incidence of HIV and syphilis among men who have sex with men (MSM) in Europe has recently increased. Rapid point-of-care tests (POCTs) for syphilis can improve access to screening. The purpose of this study was to evaluate the performance of two syphilis POCTs compared with laboratory tests among MSM. METHODS: The study was undertaken in Verona, Italy. Asymptomatic MSM, potentially exposed to syphilis, were enrolled prospectively. The POCTs evaluated were SD Bioline Syphilis 3.0 and Chembio DPP Syphilis Screen & Confirm Assay on both serum and fingerprick blood. The results of the POCTs were read by the naked eye by two independent readers and their concordance assessed. RESULTS: A total of 289 MSM were enrolled in the study. Based on laboratory tests, 35 MSM (12.1%) were TPPA-positive alone and 16 (5.5%) were both Treponema pallidum particle agglutination test (TPPA) and rapid plasma reagin (RPR)-positive. The specificities of both POCTs were above 99% on both serum and fingerstick blood specimens, while sensitivities varied considerably. The sensitivity of the SD Bioline test was lower on fingerprick blood (51.4% and 54.3%, readers 1 and 2, respectively) compared with that on serum (80.0% and 82.9%). In contrast, the Chembio test exhibited similar sensitivity values for serum and fingerprick samples (57.7% and 64.0% on serum vs 65.4% and 69.2% on fingerprick for the treponemal component; 63.6% on both samples by both readers for the non-treponemal component). The positive predictive value ranged between 100% and 93.9% for the treponemal component of both syphilis POCTs, but was lower (76.3%-100%)%) for the non-treponemal component of the Chembio POCT. The negative predictive value surpassed 90% for both tests on both samples. The agreement between readers was very high (>99%). CONCLUSION: The diagnostic performance of the syphilis POCTs was lower than expected; however, considering the prevalence of syphilis among MSM, POCTs should be recommended to improve syphilis detection among MSM.

Metaanalysis of the Performance of a Combined Treponemal and Nontreponemal Rapid Diagnostic Test for Syphilis and Yaws.

BACKGROUND: The human treponematoses are important causes of disease. Mother-to-child transmission of syphilis remains a major cause of stillbirth and neonatal death. There are also almost 100 000 cases of endemic treponemal disease reported annually, predominantly yaws. Rapid diagnostic tests (RDTs) would improve access to screening for these diseases. Most RDTs cannot distinguish current and previous infection. The Dual Path Platform (DPP) Syphilis Screen & Confirm test includes both a treponemal (T1) and nontreponemal (T2) component and may improve the accuracy of diagnosis. METHODS: We conducted a metaanalysis of published and unpublished evaluations of the DPP-RDT for the diagnosis of syphilis and yaws. We calculated the sensitivity, specificity, and overall agreement of the test compared with reference laboratory tests. RESULTS: Nine evaluations, including 7267 tests, were included. Sensitivity was higher in patients with higher titer rapid plasma reagin (≥1:16) for both the T1 (98.2% vs 90.1%, P < .0001) and the T2 component (98.2% vs 80.6%, P < .0001). Overall agreement between the DPP test and reference serology was 85.2% (84.4%-86.1%). Agreement was highest for high-titer active infection and lowest for past infection. CONCLUSIONS: The RDT has good sensitivity and specificity of the treponemal and nontreponemal components both in cases of suspected syphilis and yaws, although the sensitivity is decreased at lower antibody titers.

Evaluation of Multiplex-Based Antibody Testing for Use in Large-Scale Surveillance for Yaws: a Comparative Study.

WHO has targeted yaws for global eradication by 2020. The program goals are to interrupt the transmission in countries where yaws is endemic and to certify countries as yaws free where yaws was endemic in the past. No new rapid plasmin reagin (RPR) seroreactivity in young children is required for certification of elimination at a country level. We sought to evaluate whether antibody responses to specific treponemal antigens measured in a high-throughput multiplex bead array (MBA) assay differentiate past versus current infection and whether a nontreponemal lipoidal antigen test can be incorporated into the MBA. Serum and dried blood spot specimens collected for yaws surveillance projects in Ghana, Vanuatu, and Papua New Guinea (PNG) were run on MBA to measure antibodies against recombinant p17 (rp17) and treponemal membrane protein A (TmpA) treponemal antigens. Results were compared to standard treponemal laboratory (TPPA or TPHA [TPP(H)A]) and quantitative RPR test data. Of 589 specimens, 241 were TPP(H)A(+)/RPR(+), 88 were TPP(H)A(+)/RPR(-), 6 were TPP(H)A(-)/RPR(+), and 254 were negative for both tests. Compared to TPP(H)A, reactive concordance of rp17 was 93.7%, while reactive concordance of TmpA was only 81.9%. TmpA-specific reactivity showed good correlation with RPR titers (R(2) = 0.41; P < 0.0001). IgG responses to the lipoidal antigen used in RPR testing (cardiolipin) were not detected in the MBA. Our results suggest that TmpA can be used as a treponemal antigen marker for recent or active infection and potentially replace RPR in a high-throughput multiplex tool for large-scale yaws surveillance.

Detection of the A2058G and A2059G 23S rRNA gene point mutations associated with azithromycin resistance in Treponema pallidum by use of a TaqMan real-time multiplex PCR assay.

Macrolide treatment failure in syphilis patients is associated with a single point mutation (either A2058G or A2059G) in both copies of the 23S rRNA gene in Treponema pallidum strains. The conventional method for the detection of both point mutations uses nested PCR combined with restriction enzyme digestions, which is laborious and time-consuming. We initially developed a TaqMan-based real-time duplex PCR assay for detection of the A2058G mutation, and upon discovery of the A2059G mutation, we modified the assay into a triplex format to simultaneously detect both mutations. The point mutations detected by the real-time triplex PCR were confirmed by pyrosequencing. A total of 129 specimens PCR positive for T. pallidum that were obtained from an azithromycin resistance surveillance study conducted in the United States were analyzed. Sixty-six (51.2%) of the 129 samples with the A2058G mutation were identified by both real-time PCR assays. Of the remaining 63 samples that were identified as having a macrolide-susceptible genotype by the duplex PCR assay, 17 (27%) were found to contain the A2059G mutation by the triplex PCR. The proportions of macrolide-susceptible versus -resistant genotypes harboring either the A2058G or the A2059G mutation among the T. pallidum strains were 35.6, 51.2, and 13.2%, respectively. None of the T. pallidum strains examined had both point mutations. The TaqMan-based real-time triplex PCR assay offers an alternative to conventional nested PCR and restriction fragment length polymorphism analyses for the rapid detection of both point mutations associated with macrolide resistance in T. pallidum.

Introducing new diagnostics into STI control programmes: the importance of programme science.

Many innovative diagnostic technologies will become commercially available over the next 5-10 years. These tests can potentially transform the diagnosis of sexually transmitted infections but their introduction into control programmes can be hampered by health system constraints, and political, cultural, socioeconomic and behavioural factors. We used the introduction of syphilis rapid tests to illustrate the importance of programme science to address the gap between accruing evidence of acceptable test performance and the complexity of programme design, implementation and evaluation of test deployment to address public health needs and improve patient-important outcomes.

Prevalence and associations of genital ulcer and urethral pathogens in men presenting with genital ulcer syndrome to primary health care clinics in South Africa.

BACKGROUND: This study aimed to determine the prevalence of genital ulcer and urethral pathogens, as well as their association with clinical features, in men with genital ulcer disease (GUD) enrolled in a clinical trial. METHODS: Clinical data were collected by questionnaire. Ulcer swabs were tested for herpes simplex viruses (HSV-1/2), Treponema pallidum, Haemophilus ducreyi, and Chlamydia trachomatis L1-L3. First-pass urine was tested for urethral pathogens, namely Neisseria gonorrhoeae, C. trachomatis, Trichomonas vaginalis, and Mycoplasma genitalium. Pathogens were detected by real-time molecular assays. Blood was tested for HIV, HSV-2, and syphilis-associated antibodies. Pathogens and clinical associations were investigated using the χ test. RESULTS: A total of 615 men with GUD were recruited. Herpes simplex virus (HSV-1, 4.2%; HSV-2, 98.2%) and bacterial pathogens were detected in 451 (73.6%) and 48 (7.8%) of genital ulcers, respectively. Human immunodeficiency virus, HSV-2, and treponemal antibodies were detected in 387 (62.9%), 434 (70.6%), and 141 (23.0%) men, respectively, whereas 54 men (8.8%) were rapid plasmin reagin (RPR) seropositive. A total of 223 urethral infections were diagnosed in 188 men (30.6%), including 69 (11.2%) M. genitalium, 64 (10.4%) T. vaginalis, 60 (9.8%) C. trachomatis, and 30 (4.9%) N. gonorrhoeae infections. Dysuria was reported by 170 men (27.6%), and 69 men (11.5%) had urethral discharge on examination. Urethral pathogens were detected in 102/409 (24.9%) men without these clinical features. CONCLUSIONS: Herpes accounted for most GUD cases and urethral pathogen coinfections were common. Erythromycin, dispensed to treat infrequent chancroid and lymphogranuloma venereum cases, provided additional treatment of some asymptomatic urethral pathogens. Additional antibiotics would be required to treat asymptomatic trichomoniasis and gonorrhea.

Laboratory-confirmed case of yaws in a 10-year-old boy from the Republic of the Congo.

We report a case of yaws in a patient with puritic cutaneous eruption who was initially suspected of infection with monkeypox. The diagnosis was established by real-time PCR and sequencing of specific treponemal DNA sequences. This is the first report describing the use of DNA sequencing to identify Treponema pallidum subsp. pertenue-specific sequences in a patient with active yaws.

Cost-effectiveness of a dual non-treponemal/treponemal syphilis point-of-care test to prevent adverse pregnancy outcomes in sub-Saharan Africa.

BACKGROUND: A dual nontreponemal/treponemal point-of-care test (Dual-POC) that simultaneously detects both nontreponemal and treponemal antibodies has been developed and evaluated. In this study, we compare the health and economic outcomes of the new test with existing syphilis tests/testing algorithms in a high prevalence setting. METHODS: We used a cohort decision analysis model to examine 4 testing/screening algorithms; the Dual-POC test, the laboratory-based rapid plasma reagin and Treponema pallidum haemagglutination assay (RPR+TPHA) algorithm, an onsite RPR testing, and point-of-care treponemal immunochromatographic strip (ICS) testing. Outcomes included miscarriage, stillbirth, congenital syphilis, low birth weight, and neonatal death. Disability-adjusted life-years were estimated for all health outcomes. The analytic horizon was the life expectancy for the mother and child. RESULTS: For a cohort of 1000 pregnant women in a historically high syphilis prevalence population (10% infected and 15% previously infected), the model predicted a total of 39 adverse pregnancy outcomes if no serologic screening were performed; 13 for the laboratory-based RPR+TPHA; 11 for the on-site RPR strategy; 5 for the Dual-POC strategy; and 2 for the ICS strategy. On the basis of assumption that the cost of ICS and the Dual-POC tests were the same, the ICS strategy was the most cost saving (saved $30,000) followed by the Dual-POC strategy (saved $27,000). CONCLUSIONS: The dual-POC test may help save cost in resource-poor settings where disease prevalence (and loss to follow-up) is high, while substantially reducing overtreatment.

Serologic testing for syphilis in the United States: a cost-effectiveness analysis of two screening algorithms.

BACKGROUND: The introduction of automated treponemal enzyme immunoassays and chemiluminescence assays (EIA/CA) tests has led some laboratories in the United States to use new syphilis screening algorithms that start with a treponemal test. We compared the economic and health outcomes of this new algorithm with the standard algorithm from the perspective of the United States health system. METHODS: We used a cohort decision analysis to estimate the expected costs and effects (including follow-ups and overtreatment) of the 2 algorithms from a health-care system perspective. In the standard algorithm, rapid plasma reagin (RPR) is followed (if reactive) by EIA/CA (Nontreponemal-First). In the new algorithm, EIA/CA is followed (if reactive) by RPR. If the RPR is negative, Treponema pallidum passive particle agglutination assay (TP-PA) test is used (Treponemal-First). RESULTS: For a cohort of 200,000 individuals (1000 current infections and 10,000 previous infections), the net costs were $1.6 m (Treponemal-First) and $1.4 m (Nontreponemal-First). The Treponemal-First option treated 118 more cases (986 vs. 868) but resulted in a substantially higher number of follow-ups (11,450 vs. 3756) and overtreatment (964 vs. 38). Treating the additional 118 cases might prevent 1 case of tertiary syphilis. The estimated cost-effectiveness ratios were $1671 (Treponemal-First) and $1621 (Nontreponemal-First) per case treated. The overtreatment was a function of the specificity of the EIA/CA and the lack of independence of EIA/CA and TP-PA. CONCLUSION: The Treponemal-First option costs slightly more and results in more unnecessary treatment.

The tale of two serologic tests to screen for syphilis--treponemal and nontreponemal: does the order matter?

BACKGROUND: Standard syphilis screening involves an initial screening with a nontreponemal test and confirmation of positives with a treponemal test. However, some laboratories have reversed the order. There is no detailed quantitative and qualitative evaluation for the order of testing. In this study, we analyzed the health and economic outcomes of the order of testing for the 2 serologic tests used in syphilis screening under pure screening settings. METHODS: We used a cohort decision analysis to examine the health and economic outcomes of the screening algorithms for low and high prevalence settings. The 2-step algorithms were nontreponemal followed by treponemal (Nontrep-First) and treponemal followed by nontreponemal (Trep-First). We included the 1-step algorithms (treponemal only [Trep-Only] and an on-site nontreponemal only [Nontrep-Only]) for comparison. We estimated overtreatment rates and the number of confirmatory tests required for each algorithm. RESULTS: For a cohort of 10,000 individuals, our results indicated that the overtreatment rates were substantially higher (more than 3 times) for the 1-step algorithms, although they treated a higher number of cases (over 15%). The 2-step algorithms detected and treated the same number of individuals. Among the 2-step algorithms, the Nontrep-First was more cost-effective in the low prevalence setting ($1400 vs. $1500 per adverse outcome prevented) and more cost-saving ($102,000 vs. $84,000) in the high prevalence setting. CONCLUSIONS: The difference in cost was largely due to the substantially higher number of confirmatory tests required for the Trep-First algorithm, although the number of cases detected and treated was the same.

Evaluation of three serological tests manufactured in Belarus for the diagnosis of syphilis.

The performance of three serological tests manufactured in Belarus for the diagnosis of syphilis, i.e. a microprecipitation reaction (MPR) and two enzyme-linked immunosorbent assays (ELISAs) were compared with internationally recognized assays, namely the rapid plasma reagin test and the Treponema pallidum passive particle agglutination assay (TPPA). Sera from 392 consecutive patients attending Brest (Belarus) regional dermatovenereological dispensaries were tested. The sensitivity of the MPR test was low (77.3%) compared with the rapid plasma reagin test, while the specificity was high (100%). In contrast, both Belarusian ELISAs performed well when compared with the TPPA (sensitivities of 99.2% and 100%, specificities of 98.7% and 99.0%, respectively). There is a clear need to improve the sensitivity of the existing Belarusian MPR test or to use a more sensitive screening test in order to improve diagnosis of the disease in Belarus.

Survey of diagnostic services for genital herpes in fourteen countries in Eastern Europe.

This paper reports survey-based data on the diagnosis and management of genital herpes simplex virus (HSV) infection in 14 countries of the Eastern European Network for Sexual and Reproductive Health (EE SRH). Only 43% of the countries could provide the number of genital HSV cases recorded at national level. Eighty-six percent of countries employed syndromic management in cases of genital ulcer disease. Most countries performed type-specific and/or non-type-specific enzyme immunoassays to detect HSV antibodies. Non-type-specific serology for diagnostic purposes should be actively discouraged. Direct detection methods for HSV, such as PCR, antigen detection and culture, are available in the region, but their usage was extremely low. Their use in Eastern European countries should be actively promoted. The availability of laboratory services must be improved, and countries in the region should implement consensus recommendations for the laboratory diagnosis of genital HSV infections in order to improve clinical practice.

Gonococcal resistance: are cephalosporins next?

The development of resistance to multiple antibiotics has limited treatment options for gonorrhea in many countries. Currently, the Centers for Disease Control and Prevention only recommend cephalosporin antibiotics for treatment of uncomplicated gonorrhea. Although the cephalosporins remain effective, the demonstrated ability of Neisseria gonorrhoeae to develop resistance has raised concerns about the possibility of multidrug-resistant N. gonorrhoeae strains, which include cephalosporin resistance. This article provides a review of global trends in cephalosporin susceptibility among gonococcal isolates, recent findings that deepen our understanding of genetic mechanisms of resistance, and the public health and clinical implications of the potential emergence of cephalosporin-resistant gonorrhea.

Novel point-of-care test for simultaneous detection of nontreponemal and treponemal antibodies in patients with syphilis.

We describe a point-of-care immunochromatographic test for the simultaneous detection of both nontreponemal and treponemal antibodies in the sera of patients with syphilis that acts as both a screening and a confirmatory test. A total of 1,601 banked serum samples were examined by the dual test, and the results were compared to those obtained using a quantitative rapid plasma reagin (RPR) test and the Treponema pallidum passive particle agglutination (TP-PA) assay. Compared to the RPR test, the reactive concordance of the dual test nontreponemal line was 98.4% when the RPR titers of sera were ≥1:2 and the nonreactive concordance was 98.6%. Compared to the TP-PA assay, the reactive and nonreactive concordances of the treponemal line were 96.5% and 95.5%, respectively. These results indicate that the dual test could be used for the serological diagnosis of syphilis in primary health care clinics or resource-poor settings and therefore improve rates of treatment where patients may fail to return for their laboratory results.

Molecular epidemiology of syphilis--San Francisco, 2004-2007.

We describe the molecular epidemiology of syphilis in San Francisco (SF) using Treponema pallidum specimens obtained from patients examined at the SF municipal sexually transmitted diseases clinic during 2004-2007. Of 69 specimens, 52 (75%) were subtype 14d9. Single subtype predominance might reflect a closely linked sexual network in SF.

The potential of backscattering interferometry as an in vitro clinical diagnostic tool for the serological diagnosis of infectious disease.

Backscattering interferometry enables the detection of syphilis antibody-antigen interactions in the presence of human serum, showing promise as a diagnostic tool for the serological diagnosis of infectious disease with potentially quantitative capabilities.