Comparison of RPR and ELISA with TPHA for the Diagnosis of Syphilis: Implication for Updating Syphilis Point-of-Care Tests in Ethiopia

Performance Assessment of Treponemal and Nontreponemal Tests for the Diagnosis of Acquired Syphilis

There are a variety of nontreponemal test (NTT) and treponemal test (TT) kits for the serologic diagnosis of syphilis. Because of the complexity of the infection (multiple clinical stages) and the different antigens used in these kits, a systematic evaluation of the accuracy of the currently available commercial tests is warranted. Our objective was to evaluate the performance of commercially available tests for the diagnosis of syphilis infection. In this study, we analyzed one NTT (Venereal Disease Research Laboratory [VDRL] test, Wiener Laboratories, Rosario, Argentina) and two TTs (fluorescent treponemal antibody absorption [FTA-ABS] test, Euroimmun, Lübeck, Germany, and syphilis recombinant ELISA v. 4.0 test [ELISA], Wiener Laboratories, Rosario, Argentina) using a panel of 187 samples, including serum samples from 31 individuals with primary syphilis, 77 with secondary syphilis, and 79 with latent syphilis. An additional 192 samples from uninfected individuals and 323 serum samples from individuals with other diseases were included. The sensitivities of the VDRL, ELISA, and FTA-ABS tests were 97.9%, 100%, and 96.3%, respectively. The VDRL and ELISA tests showed a specificity of 100%, and the FTA-ABS test showed a specificity of 99.5%. Accuracy was 98.9% for the VDRL test, 100% for the ELISA, and 97.9% for the FTA-ABS test. For primary, secondary, and latent syphilis, the ELISA achieved a diagnostic performance of 100%, whereas the sensitivity for the VDRL and FTA-ABS tests ranged from 96.8% to 98.7% and 93.7% to 98.7%, respectively. No difference was observed when the tests were used as traditional or reverse algorithms. In general, all three tests are able to discriminate positive and negative samples for syphilis, regardless of the diagnostic algorithm.

Evaluating the diagnostic accuracy of TpN17 and TmpA recombinant proteins in syphilis detection: a phase II study

Syphilis is a sexually transmitted infection (STI) caused by the spiral bacterium Treponema pallidum. Diagnosis is based on epidemiology, clinical and serology, but serodiagnosis is challenging because distinct clinical forms of the infection may influence serological performance. Several recombinant Treponema pallidum-proteins have already been tested for syphilis diagnosis and they are critical to achieve high accuracy in serological testing. A total of 647 samples were included in the study: 180 T. pallidum-positive samples, 191 T. pallidum-negative samples and 276 sera from individuals infected with unrelated diseases. The diagnostic potential was validated by analysis of ROC curves. For the indirect ELISA, TpN17 (100%) and TmpA (99%) showed excellent AUC values. Sensitivity values were 97.2% for TpN17 and 90.6% for TmpA, while specificity was 100% for both molecules. According to the clinical phase, TmpA ranged from 84% to 97%, with the highest value for secondary syphilis. TpN17 was 100% sensitive for the primary and secondary stages and 93.2% for recent latent syphilis. All clinical phases achieved 100% specificity. Accuracy values showed that TmpA (> 95%) and TpN17 (> 98%) presented high diagnostic accuracy for all clinical stages of syphilis. Cross-reactivity was only observed in one sample positive for Chagas disease (1.5%), when TpN17 was evaluated. On the other hand, TmpA showed reactivity for two samples positive for Chagas disease (3.1%), one sample positive for HBV (1.25%), two samples positive for HIV (9.5%) and one sample positive for HTLV (1.6%). The TmpA antigen's performance was evaluated in multiple studies for syphilis diagnosis, corroborating our findings. However, TpN17 sensitivity values have ranged in other studies. According to clinical stages of the infection, our findings obtained close performance values.

Comparative evaluation of rapid plasma reagin and ELISA with Treponema pallidum hemagglutination assay for the detection of syphilis in blood donors: a single center experience

INTRODUCTION

The prime responsibility of blood transfusion services in India is to provide safe blood. The donated blood is tested for human immunodeficiency virus (HIV), hepatitis B virus (HBV), hepatitis C virus (HCV), malaria and syphilis. In India, the screening of donated blood for syphilis is performed by rapid plasma reagin (RPR) or venereal disease research laboratory (VDRL), whereas the World Health Organization (WHO) recommends screening of syphilis in blood donors by enzyme-linked immunosorbent assay (ELISA). Therefore, the aim of this study was to evaluate the performance of RPR and ELISA with the Treponema pallidum hemagglutination assay (TPHA - the gold standard) for the detection of syphilis in blood donors.

METHODS

In this cross-sectional study, 1524 consecutive whole blood donors were screened from April to October 2022. All blood samples collected during the study period were tested by RPR, ELISA and the TPHA and the results obtained were compared.

RESULTS

The seroprevalence of syphilis in blood donors in this study was 0.06% by RPR and 0.72% by ELISA and TPHA. On considering ELISA and the TPHA as the gold standard, ELISA had comparable sensitivity (100%), a higher specificity (100% vs. 99.34%), a higher positive predictive value (PPV - 100% vs. 9.1%) and no biological false positive/false negative results (0 vs. 10 false negatives) when compared to RPR.

CONCLUSION

ELISA performed better as a screening assay than RPR in the detection of syphilis in blood donors, which is in agreement with the WHO recommendations for syphilis testing in blood donors with low prevalence.

Impact of Point-of-Care Testing on the Management of Sexually Transmitted Infections in South Africa: Evidence from the HVTN702 Human Immunodeficiency Virus Vaccine Trial

BACKGROUND

Alternative approaches to syndromic management are needed to reduce rates of sexually transmitted infections (STIs) in resource-limited settings. We investigated the impact of point-of-care (POC) versus central laboratory-based testing on STI treatment initiation and STI adverse event (STI-AE) reporting.

METHODS

We used Kaplan-Meier and Cox regression models to compare times to treatment initiation and STI-AE reporting among HVTN702 trial participants in South Africa. Neisseria gonorrhoeae (NG) and Chlamydia trachomatis (CT) were diagnosed POC at eThekwini clinic and in a central laboratory at Verulam/Isipingo clinics. All clinics used POC assays for Trichomonas vaginalis (TV) testing.

RESULTS

Among 959 women (median age, 23 [interquartile range, 21-26] years), median days (95% confidence interval [95%CI]) to NG/CT treatment initiation and NG/CT-AE reporting were 0.20 (.16-.25) and 0.24 (.19-.27) at eThekwini versus 14.22 (14.12-15.09) and 15.12 (13.22-21.24) at Verulam/Isipingo (all P < .001). Median days (95%CI) to TV treatment initiation and TV-AE reporting were 0.17 (.12-.27) and 0.25 (.20-.99) at eThekwini versus 0.18 (.15-.2) and 0.24 (.15-.99) at Verulam/Isipingo (all P > .05). Cox regression analysis revealed that NG/CT treatment initiation (adjusted hazard ratio [aHR], 39.62 [95%CI, 15.13-103.74]) and NG/CT-AE reporting (aHR, 3.38 [95%CI, 2.23-5.13]) occurred faster at eThekwini versus Verulam/Isipingo, while times to TV treatment initiation (aHR, 0.93 [95%CI, .59-1.48]) and TV-AE reporting (aHR, 1.38 [95%CI, .86-2.21]) were similar.

CONCLUSIONS

POC testing led to prompt STI management with potential therapeutic and prevention benefits, highlighting its utility as a diagnostic tool in resource-limited settings.

Prevalence of reproductive tract infections among women preparing to conceive in Chongqing, China: trends and risk factors

Background

Reproductive tract infection has become a major public health issue all over the world for its high and growing prevalence. It can cause adverse pregnancy outcomes in pregnant women and their foetuses. This study aimed to investigate the trends and risk factors of the prevalence of reproductive tract infections among women who prepared to conceive in the Chongqing Municipality (China) from 2012 to 2016.

Methods

A multi-center cross-sectional study was conducted between January 2012 and December 2016. Women aged 20–49 years who intended to get pregnant were recruited for this study. All participants underwent preconception examination, which included testing for Neisseria gonorrhoeae, Chlamydia trachomatis, Trichomonas vaginalis, syphilis, bacterial vaginosis and candidiasis according to the national diagnostic standard. A total of 439,372 women with testing results for all six types of reproductive tract infections were included in our final analyses. Logistic regression and factor analysis were used to determine the possible sociodemographic factors associated with prevalence trends.

Results

In our study, the overall positive rate of RTIs among the 439,372 women of reproductive age was 5.03%. Candidiasis was the most common infection in our population (2.47%), followed by bacterial vaginosis (1.28%), syphilis (0.73%), T. vaginalis (0.49%), C. trachomatis (0.20%) and N. gonorrhoeae (0.06%). The prevalence of reproductive tract infections was highest among women aged 35 years and above, with a primary or lower education level, history of pregnancy, delivery, induced abortion, or spontaneous abortion. From 2012 to 2016, the trend of the overall prevalence of reproductive tract infections was V-shaped, decreasing steadily from 2012 to 2015, with a slight rise in 2016. Our results suggest that the distribution change of age, education level, gravidity, parity, and history of induced abortion influenced this trend.

Conclusion

Since the number of high-risk women who intend to become pregnant is growing in the Chongqing Municipality, pre-conception positive preventions including health education, regular screening, and timely treatment of reproductive tract infections are needed to prevent the impact of reproductive tract infections on maternal health and infant safety.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12978-022-01502-x.

Reproductive tract infections (RTIs) can cause serious health problems, such as spontaneous abortion and congenital diseases in pregnant women and their foetuses. However, there is a lack of studies focusing on the prevalence of RTIs and their trends among women who intend to conceive. This cross-sectional study examined data collected from 439,372 women during their preconception care to investigate the trend and related risk factors of the prevalence of RTIs, thereby providing essential data for their prevention. Participants were women from all 39 counties in the Chongqing Municipality of China, and data were collected between 2012 and 2016. We found that the overall prevalence of the six types of RTIs among these women was 5.03%, which was relatively lower than that in other populations in previous studies. Age, education level, history of pregnancy or delivery, and history of abortion were all associated with the prevalence of RTIs. The prevalence trend from 2012 to 2016 was V-shaped decreased steadily from 2012 until 2015 and rose slightly in 2016. Our data suggested that this trend might be influenced by changes in the proportion of ‘high-risk’ women, that is, women with higher age, lower education level, and a history of pregnancy or induced abortion. This study suggests that health education and regular screening are necessary to face new challenges experienced by older women or women with previous pregnancies who intended to get pregnant in recent years in China.

Enzyme-linked immunosorbent assay (ELISA) versus Venereal Disease Research Laboratory test (VDRL) and rapid plasma reagin test (RPR) for screening of syphilis in pregnant women

OBJECTIVE

To evaluate a treponemal enzyme-linked immunosorbent assay (ELISA) as an alternative screening test for syphilis in pregnant women.

METHODS

A cross-sectional study of diagnostic test accuracy was carried out in a large volume laboratory from a tertiary care center. A total of 416 serum samples, including 102 archived syphilis Treponema pallidum hemagglutination (TPHA)-positive samples and 314 samples from pregnant women, were used to determine the sensitivity and specificity of ELISA. All the samples were subjected to Venereal Disease Research Laboratory (VDRL), rapid plasma reagin (RPR), ELISA, and TPHA tests. Performance characteristics of VDRL, RPR, and ELISA were calculated with TPHA as a reference standard test.

RESULTS

VDRL and RPR exhibited higher false positivity of 10.5% and 9.6%, respectively, compared to 2.5% by ELISA. The sensitivity and specificity of ELISA were 98% and 97.5%, of VDRL were 71.6% and 89.5%, and of RPR were 73.5% and 90.5%, respectively. Moreover, ELISA had an excellent agreement (kappa=0.9) with TPHA compared to VDRL/RPR which had a moderate agreement (kappa=0.6) only.

CONCLUSION

ELISA has the potential to replace VDRL/RPR as a screening test for syphilis in centers that can perform ELISA, especially for antenatal screening.