Evaluation of INNO-LIA syphilis assay as a confirmatory test for syphilis

Evaluating chemiluminescent immunoassays for syphilis detection: A comparative analysis

BACKGROUND

Syphilis, caused by Treponema pallidum (TP), remains a significant global public health concern, with approximately 8 million new cases annually. Diagnosing syphilis is challenging due to its often-asymptomatic nature during latent stages, necessitating a combination of diagnostic methods. This study evaluates the performance of a novel chemiluminescent immunoassay (CLIA) developed by Mindray for detecting TP antibodies, comparing it to the widely used Abbott ARCHITECT Syphilis Treponemal Test (Architect-TP), the rapid plasma regain (RPR) test, and the Fujiribio INNO-LIA® Syphilis Score line immunoassay (INNO-LIA-TP).

METHODS

We selected 180 samples that exhibited agreement or discrepancies between the RPR and Architect-TP assays. The selection included 40 cases that were RPR positive and Architect-TP positive, 40 cases that were RPR positive and Architect-TP negative, and 100 cases that were negative in both RPR and Architect-TP. All samples underwent re-testing using the Mindray-TP and INNO-LIA-TP assays.

RESULTS

Mindray-TP and Architect-TP exhibited excellent sensitivity of 100 % (95 % CI: 91-100) and specificity of 100 % (95 % CI: 97.4-100), with perfect agreement (κ= 1.00) compared to INNO-LIA-TP. Notably, 40 cases (28.6 %; 40/140) demonstrated false-positive results when using the RPR test compared to INNO-LIA-TP, indicating a substantial false-positive rate for the RPR assay.

CONCLUSION

This study highlights the high diagnostic accuracy of the Mindray-TP assay, positioning it as a reliable and efficient tool for syphilis screening in high-volume laboratories. Given its operational efficiency and strong agreement with gold-standard assays, Mindray-TP can enhance diagnostic workflows, leading to timely syphilis detection and improved patient outcomes.

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.

A brief recent history of the epidemiology of congenital syphilis in the United Kingdom

Within a century, congenital syphilis has been reduced from a major cause of morbidity and mortality to a condition rarely seen in the UK. Here, newly-derived literature and information searches were used to create a contemporary overview of the epidemic, including its epidemiology. Although constrained by high-quality healthcare services and with an incidence below the World Health Organization elimination threshold, congenital syphilis still has the potential to cause major consequences for the health and life chances of affected infants. If the complex challenges presented by this preventable disease are to be resolved, intervention strategies need to be optimised, rigorously assessed and extended across Europe.

Sex differences in the significance of isolated reactive treponemal chemiluminescence immunoassay results

OBJECTIVES

The significance of sera with isolated reactive treponemal chemiluminescence immunoassay (IRTCIA) results is unclear. Women have this phenotype more commonly than men. Most cohorts examining this phenotype have included predominantly men and have demonstrated evidence of past or subsequently confirmed syphilis infection in a significant proportion of cases. We hypothesised that a proportion of sera with IRTCIA results would be positive on immunoblot testing and that sera from women with IRTCIA would have different results in immunoblot testing than men.

METHODS

IRTCIA sera from a tertiary referral serology laboratory serving multiple clinical sites were analysed with a syphilis line immunoblot assay (LIA) and analysed by sex. Logistic regression was undertaken to assess factors associated with LIA status. Medical record review and descriptive analysis of a separate cohort of women with the IRTCIA phenotype from a single campus was also undertaken.

RESULTS

Overall, 19/63 (30.1%) subjects with the IRTCIA phenotype were positive in the LIA, including 13 men and 6 women. Women were significantly less likely to have definitive results (positive or negative) than men (p=0.015). Pregnant women were less likely than non-pregnant women to have a negative LIA result (OR 0.57; p=0.03). Record review of 22 different women with IRTCIA reactivity showed that 2/22 (9.1%) had HIV and previous syphilis infection, 15/22 (68.2%) were pregnant and 3 (13.6%) had autoimmune disease.

CONCLUSIONS

A significant proportion of sera with IRTCIA results on serological tests are reactive on LIA testing and some may not be false positive results. The interpretation of IRTCIA results should be undertaken in conjunction with an assessment of factors such as sex, pregnancy, a history of syphilis and other STIs and syphilis risk.

Contribution of a Comparative Western Blot Method to Early Postnatal Diagnosis of Congenital Syphilis

Serology has a pivotal role in the diagnosis of congenital syphilis (CS), but problems arise because of the passive transfer of IgG antibodies across the placenta. The aim of this study was to assess the diagnostic value of a comparative Western blot (WB) method finalized to match the IgG immunological profiles of mothers and their own babies at birth in order to differentiate between passively transmitted maternal antibodies and antibodies synthesized by the infants against Treponema pallidum Thirty infants born to mothers with unknown or inadequate treatment for syphilis were entered in a retrospective study, conducted at St. Orsola-Malpighi Hospital, Bologna, Italy. All of the infants underwent clinical, instrumental, and laboratory examinations, including IgM WB testing. For the retrospective study, an IgG WB assay was performed by blotting T. pallidum antigens onto nitrocellulose sheets and incubating the strips with serum specimens from mother-child pairs. CS was diagnosed in 11 out of the 30 enrolled infants; 9/11 cases received the definitive diagnosis within the first week of life, whereas the remaining two were diagnosed later because of increasing serological test titers. The use of the comparative IgG WB testing performed with serum samples from mother-child pairs allowed a correct CS diagnosis in 10/11 cases. The CS diagnosis was improved by a strategy combining comparative IgG WB results with IgM WB results, leading to a sensitivity of 100%. The comparative IgG WB test is thus a welcome addition to the conventional laboratory methods used for CS diagnosis, allowing identification and adequate treatment of infected infants and avoiding unnecessary therapy of uninfected newborns.

Efforts in blood safety: Integrated approach for serological diagnosis of syphilis

Recent efforts in transfusion medicine are focused on improving blood safety as well as establishing effective and efficient diagnostic algorithms for donor screening. To date, syphilis is a transfusion-transmitted infection re-emerged in many countries as a public health threat especially among populations at specific risk. This task requires new diagnostic tools and hemovigilance programs. The current diagnostic methodologies are debated, since presenting limitations and unresolved issues with special regard to the clinical interpretation of serological patterns, especially in asymptomatic patients and in blood donors. Furthermore, the switch from the traditional to alternative diagnostic algorithms underlines the lack of a gold standard, which has not been supported by shared guidelines. Besides, a lot of ongoing clinical trials on the performance of diagnostic assays, on the serological response associated with different pharmacological treatments, as well as on the prevention programs are currently under investigation. Here, we review the recent literature about the diagnosis of syphilis especially for low-risk populations proposing the adoption of an algorithm for blood donor screening that should satisfy the need of increasing safety for transfusion-transmitted infections in the modern blood transfusion centers.

Syphilis detection: evaluation of serological screening and pilot reverse confirmatory assay algorithm in blood donors

Serological assays are still considered the most useful tests in the diagnosis of syphilis. Since no single serological assay is able to provide a satisfactory result, in our laboratory we have evaluated the usefulness of a commercially-available immunoblot to diagnose syphilis infection among blood donors. From October 2012 to June 2013, 4572 blood donors were screened for syphilis with an automated chemiluminescent microparticle immunoassay (CMIA). To confirm the presence of treponemal antibodies, CMIA-reactive sera were tested by standard Treponema pallidum haemagglutination assay (TPHA). In addition, an alternative confirmatory test - the immunoblot INNO-LIA assay was introduced in our laboratory. Since two additional positives among CMIA-reactive-TPHA-negative samples were found, we concluded that the INNO-LIA immunoblot allowed a better detection of syphilis compared to TPHA. A confirmatory strategy based on the use of two treponemal assays could meet the screening requirements for blood donors as well as in our centre.

Evaluation of treponemal serum tests performed on cerebrospinal fluid for diagnosis of neurosyphilis

OBJECTIVES

We evaluated the use of treponemal serum tests in cerebrospinal fluid (CSF) to diagnose neurosyphilis since CSF-Venereal Disease Research Laboratory (VDRL) is specific but lacks sensitivity.

METHODS

We tested CSF specimens using the following treponemal serum tests: INNO-LIA, Treponema pallidum particle agglutination (TP-PA), Trep-Sure, and Maxi-Syph. The reference standard to calculate sensitivity and specificity was having two or more reactive/positive tests on CSF.

RESULTS

The reference standard group included 11 cases that fulfilled the definition of neurosyphilis (reactive CSF-VDRL plus symptoms) and three cases that did not fulfill the definition: two cases had neurologic symptoms but a nonreactive CSF-VDRL, and one had several positive CSF syphilis tests (reactive VDRL and positive treponemal and syphilis polymerase chain reaction) but no history (referred sample). Controls included 18 patients in whom a CSF-VDRL was performed the same week as patients in the reference group. The sensitivity was 85.7% (12/14) for CSF-VDRL, 92.9% (13/14) for Trep-Sure, 100% (10/10) for Maxi-Syph, 92.3% (12/13) for INNO-LIA, and 83.3% (10/12) for TP-PA. Specificity was 100% for all tests.

CONCLUSIONS

Treponemal serum tests performed on CSF were useful in identifying two patients with nonreactive CSF-VDRL.

Recent trends in the serologic diagnosis of syphilis

Complexities in the diagnosis of syphilis continue to challenge clinicians. While direct tests (e.g., microscopy or PCR) are helpful in early syphilis, the mainstay of diagnosis remains serologic tests. The traditional algorithm using a nontreponemal test (NTT) followed by a treponemal test (TT) remains the standard in many parts of the world. More recently, the ability to automate the TT has led to the increasingly widespread use of reverse algorithms using treponemal enzyme immunoassays (EIAs). Rapid, point-of-care TTs are in widespread use in developing countries because of low cost, ease of use, and reasonable performance. However, none of the current diagnostic algorithms are able to distinguish current from previously treated infections. In addition, the reversal of traditional syphilis algorithms has led to uncertainty in the clinical management of patients. The interpretation of syphilis tests is further complicated by the lack of a reliable gold standard for syphilis diagnostics, and the newer tests can result in false-positive reactions similar to those seen with older tests. Little progress has been made in the area of serologic diagnostics for congenital syphilis, which requires assessment of maternal treatment and serologic response as well as clinical and laboratory investigation of the neonate for appropriate management. The diagnosis of neurosyphilis continues to require the collection of cerebrospinal fluid for a combination of NTT and TT, and, while newer treponemal EIAs look promising, more studies are needed to confirm their utility. This article reviews current tests and discusses current controversies in syphilis diagnosis, with a focus on serologic tests.

Canadian Public Health Laboratory Network laboratory guidelines for the use of serological tests (excluding point-of-care tests) for the diagnosis of syphilis in Canada

Syphilis, caused by the bacterium Treponema pallidum subsp. pallidum, is an infection recognized since antiquity. It was first reported at the end of the 15th century in Europe. Infections may be sexually transmitted as well as spread from an infected mother to her fetus or through blood transfusions. The laboratory diagnosis of syphilis infection is complex. Because this organism cannot be cultured, serology is used as the principal diagnostic method. Some of the issues related to serological diagnoses are that antibodies take time to appear after infection, and serology screening tests require several secondary confirmatory tests that can produce complex results needing interpretation by experts in the field. Traditionally, syphilis screening was performed using either rapid plasma reagin or Venereal Disease Research Laboratory tests, and confirmed by treponemal tests such as MHA-TP, TPPA or FTA-Abs. Currently, that trend is reversed, ie, most of the laboratories in Canada now screen for syphilis using treponemal enzyme immunoassays and confirm the status of infection using rapid plasma reagin or Venereal Disease Research Laboratory tests; this approach is often referred to as the reverse algorithm. This chapter reviews guidelines for specimen types and sample collection, treponemal and non-treponemal tests utilized in Canada, the current status of serological tests for syphilis in Canada, the complexity of serological diagnosis of syphilis infection and serological testing algorithms. Both traditional and reverse sequence algorithms are recommended and the algorithm used should be based on a combination of local disease epidemiology, test volumes, performance of the proposed assays and available resources.

From little helpers to automation

Western blot technology has continually evolved to enhance sensitivity, speed, and ease of operation. For enhancing awareness to these developments, this brief review outlines a representative selection of methods and devices, many of which are commercial products. In particular, the steps taken towards partial and full automation of western blotting are addressed.

Establishment and Evaluation of a One-Step Microplate Chemiluminescence Immunoassay to Detect IgG Antibody Against Treponema Pallidum

BACKGROUND

The serological detection of specific antibodies against Treponema pallidum is of particular importance in the diagnosis of syphilis. The chemiluminescence immunoassay (CLIA) has been widely used for clinical diagnosis because they remit no radical waste products, cause no enzyme precipitation, and exhibit an excellent sensitivity.

METHODS

A one-step CLIA was established to detect T. pallidum IgG antibody based on microplate coated with a mixture of recombinant T. pallidum antigens TpN15, TpN17, and TpN47. The Chinese national reference substances standard panel for T. pallidum diagnosis was applied to test the accuracy, stability, interference, and cross-reactivity of the established CLIA. The validation of efficacy for clinical application was performed by comparing the established method with the marketed T. pallidum particle agglutination (TPPA) kit and the Abbott ARCHITEC Auto System.

RESULTS

The established method met the requirement of the Chinese national reference substances standard for T. pallidum diagnosis. When compared with TPPA (n = 1,052), the specificity, sensitivity, and overall concordance were 99.7%, 99.0%, and 98.8% respectively, showing a great agreement with a kappa value of 0.81. When compared with the Abbott ARCHITEC Auto System (n = 352), the results showed that the specificity, sensitivity, and overall concordance were 98.6.0%, 96.6% and 98.6% respectively, and a high-degree agreement was observed (kappa value = 0.95).

CONCLUSION

The established rapid, specific, sensitive, and stable microplate CLIA method to detect IgG antibody against T pallidum will provide an efficient alternative to the treponemal tests and wide application in clinical laboratory.

Determination of class M and G antibodies to T.pallidum antigens in patients with primary syphilis

The authors present the results of a study of blood serum samples obtained from patients with clinically diagnosed primary syphilis by the linear immunoblotting method to determine IgM and IgG antibodies to T. pallidum antigens, which enabled the authors to study the intensity of the humoral immune response to individual T. pallidum antigens at early stages of the infection. The humoral response by means of the synthesis of specific class M antibodies in case of primary syphilis was accompanied by the formation of Class G antibodies in most cases; the frequency of revealing Class M and G antibodies was as follows: TmpA antigen 100 and 98.68%; TpN47 90.79 and 97.37%; TpN17 90.79 and 89.47%; TpN 15 72.37 and 73.69% of all cases, respectively; the content of class G antibodies to each of the four T. pallidum antigens exceeded the levels of Class M antibodies by more than twice. Different profiles of the humoral immune response with the involvement of IgM and IgG antibodies distinguished by a more expressed synthesis of antibodies to any or several of T. pallidum antigens were discovered and characterized for the first time. The clinical sensitivity of the IgM immunoblotting method for diagnosing primary syphilis amounted to 85.53%, IgG immunoblotting 92.11%, which means that the method can be used to diagnose early forms of syphilis.

Use of the INNO-LIA syphilis score assay in the resolution of discordant positive screening enzyme immunoassay results for the serological diagnosis of syphilis

We studied the use of the INNO-LIA syphilis score assay in the resolution of discordant positive screening results of the Murex ICE Syphilis enzyme immunoassay (EIA) with the confirmatory results of both the Serodia Treponema pallidum particle agglutination (TPPA) and the fluorescent treponemal antibody-absorption (FTA-Abs) assays, for the serological diagnosis of syphilis. This was an observational study on the serum samples received by the Syphilis Laboratory, Hong Kong, during the period from January 2006 to December 2012. A total of 801 serum samples with discordant positive screening EIA results were used. Consensus results of such serum samples were derived from results of the EIA, TPPA and FTA-abs assays. The age range of the individuals was 14 to 104 years (median of 52). There were 369 males and 432 females. Of 378 serum samples, 139 showed agreement among positive results, 23 of 310 showed agreement among indeterminate results and 277 of 465 showed agreement among negative results. The proportions of agreement among positive, indeterminate and negative results were 0.37 (95% CI 0.32–0.42), 0.07 (95% CI 0.05–0.11) and 0.60 (95% CI 0.55–0.64), respectively; kappa 0.55 (95% CI 0.49–0.60). There were 60 serum samples with positive consensus results but negative INNO-LIA syphilis score results and 10 with negative consensus results but positive INNO-LIA syphilis score results. Although the INNO-LIA syphilis score assay can be considered a valid alternative confirmatory test for the serological diagnosis of syphilis, the present study showed that its use in the resolution of discordant positive screening EIA results was moderate. A more extensive characterization of serum samples with discordant reactive screening treponemal test results is necessary.

Comparative study of Treponemal and non-Treponemal test for screening of blood donated at a blood center

The non-Treponemal tests such as Rapid Plasma Reagin test (RPR) or the Venereal Disease Reference Laboratory test are the most commonly used test for screening of syphilis in the blood centers in India. Now, with the availability of Enzyme-linked immunosorbent assay (ELISA) and Immunochromatographic assays in the market, we decided to evaluate these assays in comparison with Treponema pallidum Haemagglutination Assay (TPHA) which was considered as a gold standard for this study. A total of 8 685 samples of voluntary blood donors were tested on Trepolisa 3.0 and then the initially reactive samples were retested in duplicate on the same assay as well as on Omega Pathozyme, RPR, RAPHA (Rapid Anti-Treponema pallidum Assay), and TPHA. Of the 158 initially reactive samples, 104 were repeatedly reactive on the same assay, 85 were reactive with RPR, 77 were reactive with RAPHA, 60 were reactive on Omega, and 53 were confirmed reactive on TPHA. 48 (56.4%) of the results on RPR were biological false positive, while 21.9% of results were false negative on RPR. We evaluated that Omega Pathozyme was quite in agreement with TPHA as compared with Trepolisa 3.0, RAPHA, and RPR. We concluded that Omega Pathozyme (ELISA) can be considered as a suitable test for screening of syphilis in a blood center.

Impact of reverse sequence syphilis screening on new diagnoses of late latent syphilis in Edmonton, Canada

After the introduction of reverse sequence syphilis screening in Alberta, Canada, there was an increase in the diagnosis of late latent syphilis in individuals screening positive with the treponemal test; these cases required additional public health follow-up.

The laboratory diagnostics of syphilis: yesterday, today, tomorrow

The article covers issues related to the development of laboratory methods used for the diagnostic of syphilitic infection in the historical aspect as well as for the nearest and remote future. Priorities of the application of several diagnostic methods have been highlighted depending on the stage and form of syphilis, on the performed specific treatment and the contingent of examined patients. The authors give recommendations for its use reflected in modern Russian and foreign manuals and standards of syphilis diagnostics. Laboratory methods such as immunochemiluminescence assay, хМАР-technology and aspects of their clinical application are specially highlighted. The authors provide data on applied methods of molecular typing of Т. pallidum and detection of genetic determinants of the resistance of the syphilis pathogen to antimicrobial substances.

The immunopathobiology of syphilis: the manifestations and course of syphilis are determined by the level of delayed-type hypersensitivity

Syphilis has plagued mankind for centuries and is currently resurgent in the Western hemisphere. Although there has been a significant reduction of tertiary disease and recognition of facilitative interactions with human immunodeficiency virus infection, the natural history of syphilis has remained largely unchanged; thus, new strategies are required to more effectively combat this pathogen. The immunopathologic features of experimental syphilis in the rabbit; the course, stages, and pathology of human syphilis; and a comparison of human syphilis with leprosy suggest that the clinical course of syphilis and its tissue manifestations are determined by the balance between delayed-type hypersensitivity (DTH) and humoral immunity to the causative agent, Treponema pallidum. A strong DTH response is associated with clearance of the infecting organisms in a well-developed chancre, whereas a cytotoxic T-cell response or strong humoral antibody response is associated with prolonged infection and progression to tertiary disease. Many of the protean symptoms/appearances of secondary and tertiary human syphilis are manifestations of immune reactions that fail to clear the organism, due to a lack of recruitment and, more importantly, activation of macrophages by sensitized CD4 T cells. The Bacillus Calmette-Guerin vaccination can enhance DTH and has been shown to produce a low, but measurable, beneficial effect in the prevention of leprosy, a disease that shows a disease spectrum with characteristics in common with syphilis. In the prevention of syphilis, a potential vaccine protective against syphilis should be designed to augment the DTH response.

Modern approaches and prospects of development of laboratory diagnostics for sexuallytransmitted infections

The authors provide a comparison of modern approaches to the use of well-known laboratory methods for diagnostics of syphilis, gonorrhea, trichomoniasis and urogenital clamidiosis, which are approved in the world science and practice. They also examine promising directions in the development of up-to-date laboratory technologies (biomicrochips, multiprimer PCR, mass spectrometry, PLEX-ID technology, immunoblotting, chemiluminescence immunoassay (CLIA), xMAP, pyrosequencing) for detecting STD pathogens, which is necessary to make an etiological diagnosis and determine efficient methods of treatment minimizing the period of time required for examination of patients.

Using the Line Blot Syphilis test system for diagnosingsyphilis by the linear immunoblotting method

ZAO ECOlab (Russia) developed Line Blot Syphilis, a new test system on the basis of the linear immunoblotting method using Treponema рallidum recombinant antigens. The article assessed the diagnostic value of the Line Blot Syphilis test system in the form of a confirmatory test. As a part of the conducted study, the test system demonstrated its absolute sensitivity and specificity to serum-positive (n = 237) and serum-negative (n = 114) samples, in which the presence or absence of Т.pallidum antibodies was confirmed by two treponemal tests. As a result of examining 14 samples attributed to doubtful analytes based on two test results (passive hemagglutination test and immunofluorescence test with absorption), the data compliance between the Line Blot Syphilis test system and data from INNO-LIA Syphilis Score amounted to 100% (14/14) or 93% (13/14) for the immune-enzyme assay and 57% (8/14) for the immunofluorescence test with absorption. It is recommended to use the Line Blot Syphilis test system (ZAO ECOlab) as a confirmatory syphilis test.

Comparative evaluation of the INNO-LIA syphilis score and the MarDx Treponema pallidum immunoglobulin G Marblot test assays for the serological diagnosis of syphilis

We evaluated the performance of two immunoblot assays: the INNO-LIA Syphilis Score (LIA) and the MarDx T. pallidum IgG Marblot Test (TWB), as compared with that of the Murex ICE Syphilis enzyme immunoassay (EIA), the Serodia Treponema pallidum particle agglutination (TPPA) assay and the fluorescent treponemal antibody-absorption (FTA-abs) assay, for the serological diagnosis of syphilis using serum samples of 135 attendees of the social hygiene clinics of the Department of Health in Hong Kong newly diagnosed with syphilis and provided with clinical stages (39 in primary, 20 in secondary, 18 in early latent and 58 in latent of unknown duration) and of 43 normal healthy subjects between October and December 2004. The differences in the overall sensitivities of the LIA assay and the EIA/TPPA/FTA-abs assays were not statistically significant ( P > 0.05) whereas the overall sensitivity of the TWB assay was significantly lower ( P < 0.05) than the overall sensitivities of the EIA, the TPPA and the FTA-abs assays. The LIA assay had an overall sensitivity of 94.1% (95% CI 88.7–97.0%) whereas the TWB assay 65.2% (95% CI 56.8–72.7%). Both the LIA and the TWB assays have a specificity of 100%. When consensus results were derived from the most predominant results of the EIA, the TPPA and the FTA-abs assays, the LIA assay had a positive agreement with the consensus results of 98.5% (95% CI 94.5–99.6%) whereas the TWB assay 68.2% (95% CI 59.8–75.6%). Therefore, the LIA assay performed significantly better ( P < 0.05) than the TWB assay. The LIA assay can be considered to be a valid alternative confirmatory test for the serological diagnosis of syphilis.

[Evaluation of automated architect syphilis TP as a diagnostic laboratory screening test for syphilis]

BACKGROUND

The aim of the study was to establish a new syphilis test algorithm using Architect Syphilis TP (Abbott Japan, Japan: AST), a fully automated treponemal antibody test, as a screening test in a university hospital laboratory. We evaluated performance characteristics of AST in various patient groups.

METHODS

A total of 1,357 serum samples obtained from patients at a university hospital from June to August, 2008 were categorized into checkup, preoperative, other diseases, diagnosis (clinically suspected of syphilis), and follow up groups. We compared the results of AST with those of RPR (N=1,276) or Treponema pallidum hemagglutination assay (TPHA, N=81). Samples with discrepant results between RPR or TPHA and AST were retested by fluorescent treponemal antibody absorption test (FTA-ABS) and all patients' clinical records were thoroughly reviewed.

RESULTS

The positive rate of AST was significantly higher than that of RPR in preoperative and other diseases groups and was the same as that of RPR in diagnosis group. There were no significant differences in check up and follow up groups. The results of AST showed 97.4% (1,243/1,276) and 97.5% (79/81) concordance rates with those of RPR and TPHA, respectively. Among 26 RPR-AST discrepant and FTA-ABS confirmed cases, there were 20 RPR false-negatives, 4 RPR false-positives, 1 AST false-negative, and 1 AST false-positive.

CONCLUSIONS

Based on the results and literature review, we established a new syphilis test algorithm using AST as a screening test, which would be helpful for detection of more syphilis patients including latent infections.

Cost effectiveness of enzyme immunoassay and immunoblot testing for the diagnosis of syphilis

The burden of disease and associated health-care costs of syphilis are significant despite widespread screening and treatment. Our objective was to conduct an economic evaluation using a simulation model when comparing enzyme immunoassay (EIA) initial testing and Inno-Lia (IL) confirmatory testing (EIA + IL) with rapid plasma reagin (RPR) initial testing and Treponema pallidum particle agglutination assay (TPPA) and fluorescent treponemal antibody absorption assay (FTA-ABS) confirmatory testing (RPR + TPPA/FTA). Estimates of prevalence, test costs and utilization of services for 2006 were derived from Alberta databases. Estimates of test characteristics were derived from the available literature. The incremental cost-effectiveness ratio was Canadian $461 per additional correct diagnosis (less costly and more effective). EIA + IL is cost-effective when compared with RPR + TPPA/FTA for screening and diagnosis of syphilis.

Serological diagnosis of syphilis: comparison of the Trep-Chek IgG enzyme immunoassay with other screening and confirmatory tests

The Trep-Chek IgG Enzyme Immunoassay (Trep-Chek IgG EIA) was evaluated with 604 serum specimens submitted for syphilis serology from patients across Canada against a battery of conventional syphilis serology tests, including the Rapid Plasma Reagin (RPR) test, the Venereal Disease Research Laboratory (VDRL) test, the Treponema pallidum passive particle agglutination (TP-PA) test, the fluorescent treponemal antibody absorption (FTA-ABS) test, and the newer confirmatory test, Innogenetics INNO-LIA. On the basis of a consensus result derived from these serologic tests, 34 specimens were found to be syphilis-positive (28 active and six past infections), and 570 were syphilis-negative (including 12 biological false positives). When the test results on this set of samples were compared to those obtained with the conventional tests RPR, VDRL, TP-PA, and FTA-ABS, the sensitivity and specificity of the Trep-Chek IgG EIA were found to be 85.3% and 95.6%, respectively. Without further evaluation, we do not recommend use of the Trep-Chek IgG EIA as a stand-alone test for either screening or confirmatory syphilis serology.

Comparative evaluation of 15 serological assays for the detection of syphilis infection

Fifteen commercial syphilis kits were assessed against the same moderately sized specimen panel that included 114 serum and plasma specimens from syphilis cases and 249 specimens from unselected blood donors. The 114 specimens from syphilis cases comprised 40 from cases of primary syphilis, 43 from cases of secondary syphilis, 19 from cases of early latent syphilis, and 12 from cases of late latent syphilis. Of the 15 kits, ten were enzyme immunoassays, four were Treponema pallidum haemagglutination assays, and one was a T. pallidum particle agglutination assay. Thirteen of the 15 kits gave final specificities of 100%; the other two kits were repeatedly reactive with one to two specimens. Initial sensitivities ranged from 93.9 to 99.1%. Most variation between kits was observed in results for the groups with untreated primary and treated late latent disease, although the differences were not statistically significant. The comparative data on kit performance derived from this study is useful for examining syphilis testing guidelines and for making informed purchasing decisions.

Current Controversies in the Management of Adult Syphilis

Clinical management of patients with syphilis is controversial. This article summarizes recent research on syphilis treatment efficacy and outcomes and is based on a comprehensive systematic review of published literature, relevant abstracts, conference proceedings, technical reports, and guidelines. Penicillin remains the drug of choice for the treatment of syphilis. Although several studies have suggested that azithromycin may have clinical efficacy, macrolide resistance has been widely documented among strains of Treponema pallidum, and treatment failures have been reported. Ceftriaxone is effective for the treatment of syphilis when used in multiple-dose regimens. Lumbar puncture should be performed for human immunodeficiency virus-infected patients with syphilis of >1 year's duration and a serum nontreponemal test titer > or =1 : 32, as well for other patients for whom the clinical suspicion of neurosyphilis is high. Newer laboratory tests for syphilis are undergoing extensive evaluation and may prove to be useful for future clinical care. American and European approaches to syphilis treatment are similar, but they vary across several parameters.

Evaluation of a new particle gel immunoassay for determination of antibodies against Treponema pallidum

A new particle gel immunoassay (DiaMed AG, Cressier sur Morat, Switzerland) with three recombinant Treponema pallidum antigens was evaluated with serum samples from patients with syphilis (n = 124) and patients without syphilis (n = 490). It proved to be a simple, rapid (20 min), and useful test with sensitivity, specificity, and positive and negative predictive values of 91.9, 99.8, 99.2, and 98%, respectively.

Evaluation of a Treponema pallidum-Specific IgM Enzyme Immunoassay and Treponema pallidum Western Blot Antibody Detection in the Diagnosis of Maternal and Congenital Syphilis

BACKGROUND

Congenital syphilis (CS) is a result of untreated or inadequately treated maternal syphilis. CS is more likely with early stages of maternal syphilis, but most mothers lack signs or symptoms and the risk of CS is unclear.

GOAL

The goal of this study was to evaluate Treponema pallidum IgM Western blot (TP IgM WB) and a T. pallidum IgM enzyme immunoassay (TP IgM ELISA) in mothers with syphilis to determine if positive tests better indicate a risk of CS than a rapid plasma reagin titer >/=1:16.

STUDY DESIGN

Ninety-seven mother-baby pairs with reactive syphilis serology were evaluated.

RESULTS

TP IgM WB tests were positive in 18 pregnancies (7 of 18 babies had CS) and negative in 79 pregnancies (7 of 82 babies had CS). Thirty-two mothers had titers >/=1:16 (6 babies with CS) and 65 mothers had titers </=1:8 (8 babies with CS).

CONCLUSION

TP IgM tests better identify mothers at risk of delivering babies with CS than maternal titer >/=1:16.

Serodiagnosis of syphilis: antibodies to recombinant Tp0453, Tp92, and Gpd proteins are sensitive and specific indicators of infection by Treponema pallidum

Syphilis serodiagnosis relies on a combination of nonspecific screening tests (antilipoidal antibodies) and Treponema pallidum-specific tests (anti-T. pallidum antibodies). We studied a group of six recombinant T. pallidum antigens for their sensitivities and specificities with sera from individuals with syphilis (n = 43), relapsing fever (n = 8), Lyme disease (n = 8), and leptospirosis (n = 9) and from uninfected individuals (n = 15). Three recombinant proteins, Tp0155, Tp0483, and Tp0751, demonstrated sensitivity values that ranged from 28 to 42%. In contrast, three other recombinant proteins exhibited the following sensitivity and specificity values: Tp0453, 100% sensitivity and 100% specificity; Tp92 (Tp0326), 98% sensitivity and 97% specificity; and Gpd (Tp0257), 91% sensitivity and 93% specificity. Tp0453, Tp92, and Gpd also were recognized by sera from individuals with early primary syphilis that were nonreactive with the antilipoidal Venereal Disease Research Laboratory test. The reactivities of syphilis patient sera with Tp0453, Tp92, and Gpd were proportional to the titers of these sera with the treponemal test MHA-TP (microhemagglutination assay for T. pallidum). Thus, the recombinant T. pallidum antigens Tp0453, Tp92, and Gpd show promise as diagnostic antigens in the enzyme-linked immunosorbent assay-based assay.

Crystal structure of the 47-kDa lipoprotein of Treponema pallidum reveals a novel penicillin-binding protein

Syphilis is a complex sexually transmitted disease caused by the spirochetal bacterium Treponema pallidum. T. pallidum has remained exquisitely sensitive to penicillin, but the mode of action and lethal targets for beta-lactams are still unknown. We previously identified the T. pallidum 47-kDa lipoprotein (Tp47) as a penicillin-binding protein (PBP). Tp47 contains three hypothetical consensus motifs (SVTK, TEN, and KTG) that typically form the active center of other PBPs. Yet, in this study, mutations of key amino acids within these motifs failed to abolish the penicillin binding activity of Tp47. The crystal structure of Tp47 at a resolution of 1.95 A revealed a fold different from any other known PBP; Tp47 is predominantly beta-sheet, in contrast to the alpha/beta-fold common to other PBPs. It comprises four distinct domains: two complex beta-sheet-containing N-terminal domains and two C-terminal domains that adopt immunoglobulin-like folds. The three hypothetical PBP signature motifs do not come together to form a typical PBP active site. Furthermore, Tp47 is unusual in that it displays beta-lactamase activity (k(cat) for penicillin = 271 +/- 6 s(-1)), a feature that hindered attempts to identify the active site in Tp47 by co-crystallization and mass spectrometric techniques. Taken together, Tp47 does not fit the classical structural and mechanistic paradigms for PBPs, and thus Tp47 appears to represent a new class of PBP.