Modelling the risk of transfusion-transmitted syphilis: a reconsideration of blood donation testing strategies

Improved efficiency using sequential automated immunoassays for syphilis screening in blood donors

Using sequential immunoassays for the screening of blood donors is well described for viral serology testing but not for the screening of syphilis. In this study, we report the evaluation results and 2-year sequential testing data using two highly sensitive automated serology assays, the Alinity s Syphilis chemiluminescent immunoassay for screening, with all repeatedly reactive samples then tested on the Elecsys Syphilis electrochemiluminescence immunoassay. We screened 1,767,782 blood donor samples between 7 July 2021 and 6 July 2023 and found the Alinity false-positive rate to be low at 0.08% (1,456/1,767,782). The common false-positive rate between the two assays was also low (3.83%, 58/1,514). Concordantly reactive samples were further tested using a Treponema pallidum particle agglutination test, a rapid plasma reagin test, and a fluorescent treponemal antibody absorption test. There were 262/1,376 concordantly reactive Alinity and Elecsys blood donor samples with reactivity on one or more of the confirmatory tests. A total of 26/1,376 donors had a current syphilis infection, 152/1,376 reported a past history of syphilis and had been treated, and 84/1,376 did not report a past history of syphilis. We suggest that future studies could explore the use of sequential immunoassays to aid in the serodiagnosis for syphilis.

IMPORTANCE

The serodiagnosis for syphilis usually follows two methodologies-a "traditional" algorithm using a non-treponemal test followed by confirmation using a treponemal test, or a "reverse" algorithm using a treponemal test followed by a non-treponemal test. There are limited reports in the literature of using a modified reverse algorithm (treponemal test followed by a second treponemal test), and to the best of knowledge, there are currently no published articles using two highly sensitive automated immunoassays to aid the serodiagnosis of syphilis. In addition, the Treponema pallidum particle agglutination (TPPA) assay is commonly used as a confirmatory test for the diagnosis of syphilis. With the withdrawal of the TPPA assay from Australia and presumably from the global market also, alternative testing algorithms are now required. This study provides proof of concept for using sequential immunoassays in the diagnosis of syphilis.

Syphilis testing in blood donors, France, 2007 to 2022

BackgroundSyphilis in blood donors (BD) has increased in many countries.AimWe aimed to describe trends in syphilis seroposivity in BD in France, to identify risk factors and assess if a non-treponemic test (NTT) could define BD having recovered from syphilis for more than 1 year.MethodsThe analysis covered the period 2007 to 2022 and 45,875,939 donations. Of the 474 BD syphilis-positive in 2022, 429 underwent additional investigations with an NTT. History of syphilis was obtained at the post-donation interview or based on serology results for repeat donors.ResultsUntil 2021, positivity rates remained stable (mean: 1.18/10,000 donations, range: 1.01-1.38). An increased rate was observed in 2022 (1.74/10,000; p = 0.02). Over the whole study period, prevalence was 2.2 times higher in male than in female BD (4.1 times higher in 2022). The proportion of males with an identified risk factor who have sex with men increased from 16.7% in 2007 to 64.9% in 2022. Based on NTT, 79 (18%) of the donors who were seropositive in 2022 were classified as having been infected in the previous year. History of syphilis was available for 30 of them. All had an infection within the previous 3 years. Among seven donors with a syphilis < 12 months before testing, one had an NTT titre ≥ 8, three a titre between 1 and 4, three were negative.ConclusionSyphilis seropositivity increased considerably in BDs in 2022, mostly in males, notably MSM. Available data did not allow appropriate evaluation of the NTT to distinguish recent from past infection.

Blood safety markers in Dutch donors after relaxation of deferral for men who have sex with men: re-emergence of syphilis and HIV pre-exposure prophylaxis use

BACKGROUND

Less discriminatory donor selection policies for men who have sex with men (MSM) may impact transfusion safety in terms of higher residual risks for known transfusion-transmitted infections (TTIs), increased vulnerability toward new TTIs that are also transmitted via sex, and HIV infections masked by pre-exposure prophylaxis (PrEP).

STUDY DESIGN AND METHODS

TTI trends in Dutch donors were studied over a 13-year period (2011-2023), characterized by successive relaxations of MSM deferral criteria. Structured posttest counseling was performed to determine risk factors in TTI-positive donors. PrEP drug levels were measured in 9977 donations from male donors living in urban areas and in 67 donors with active or resolved syphilis.

RESULTS

HIV incidence (from 5.8 to 1.5 per 1,000,000 donor years (DY)) and HBV incidence (from 12.4 to 4.5 per 1,000,000 DY) in Dutch donors decreased with less stringent MSM deferral criteria, while syphilis prevalence (from 26.4 to 44.1 per 100,000 new donors) and syphilis incidence (from 18.3 to 46.3 per 1,000,000 DY) increased over time. The proportion of MSM-related syphilis rose from 2% to 32% in new donors and from 12% to 27% in repeat donors. PrEP was detected in 2 of 9977 (0.02%) donations from male donors living in urban areas, and in 1 of 39 (2.6%) male donors with syphilis.

DISCUSSION

To date, phasing out donor deferral for MSM had no significant impact on transfusion safety in the Netherlands. However, rising syphilis rates and (recent) PrEP use in the blood donor population, albeit rare, suggest an influx of donors with higher sexual risk profiles and requires intensified TTI surveillance in donors.

Does cold storage of blood before transfusion prevent the transmission of syphilis? A systematic review and meta-analysis

BACKGROUND AND OBJECTIVES

Although screening of donated blood for syphilis is almost universally applied, its cost-effectiveness is questioned because of the low prevalence of transfusion-transmitted syphilis and a widespread belief that the syphilis-causing bacterium Treponema pallidum is very vulnerable to cold storage. Since the latter claim is not yet supported by a systematic review, we investigated whether syphilis can be transmitted via transfusion following prolonged (cold or room temperature) storage of blood products.

MATERIALS AND METHODS

MEDLINE, PMC and NCBI bookshelf (PubMed interface), Cochrane Library, Embase, Web of Science and CINAHL were searched up to 17 January 2023.

RESULTS

Nine experimental animal studies and one observational human study were included. Meta-analysis showed that storing artificially infected human (six studies; risk ratio [RR] = 0.37, 95% confidence interval [CI]: 0.22-0.64, p = 0.0003) or rabbit (two studies; RR = 0.08, 95% CI: 0.01 to 0.55, p = 0.01) blood for more than 72 h before intratesticular injection significantly decreased the number of recipient animals that develop syphilis. Nonetheless, the possibility of syphilis transmission remained for up to 7 days. Differences could not be found for rabbit plasma (p = 0.60) or naturally infected rabbit blood (p = 0.28). There was limited evidence from one study in favour of the storage of artificially infected human platelets for over 72 h at cold temperatures (RR = 0.13, 95% CI: 0.03-0.52, p = 0.004) but not at room temperature (p = 0.12).

CONCLUSION

Even though the infectivity of T. pallidum-spiked blood may decrease after 72 h of cold storage, the possibility for transfusion-transmitted syphilis may remain for several days after. The evidence is very uncertain, and conclusions are hindered by a lack of sufficiently powered studies and studies in humans. In addition, T. pallidum concentrations used in animal studies may be unrealistically high.

Ignored and undervalued in public health: a systematic review of health state utility values associated with syphilis infection

BACKGROUND

Syphilis is a sexually transmitted infection causing significant global morbidity and mortality. To inform policymaking and economic evaluation studies for syphilis, we summarised utility and disability weights for health states associated with syphilis.

METHODS

We conducted a systematic review, searching six databases for economic evaluations and primary valuation studies related to syphilis from January 2000 to February 2022. We extracted health state utility values or disability weights, including identification of how these were derived. The study was registered in the international prospective register of systematic reviews (PROSPERO, CRD42021230035).

FINDINGS

Of 3401 studies screened, 22 economic evaluations, two primary studies providing condition-specific measures, and 13 burden of disease studies were included. Fifteen economic evaluations reported outcomes as disability-adjusted life years (DALYs) and seven reported quality-adjusted life years (QALYs). Fourteen of 15 economic evaluations that used DALYS based their values on the original Global Burden of Disease (GBD) study from 1990 (published in 1996). For the seven QALY-related economic evaluations, the methodology varied between studies, with some studies using assumptions and others creating utility weights or converting them from disability weights.

INTERPRETATION

We found a limited evidence base for the valuation of health states for syphilis, a lack of transparency for the development of existing health state utility values, and inconsistencies in the application of these values to estimate DALYs and QALYs. Further research is required to expand the evidence base so that policymakers can access accurate and well-informed economic evaluations to allocate resources to address syphilis and implement syphilis programs that are cost-effective.

Evolving deferral criteria for blood donation in France: Plasma donation by men who have sex with men

BACKGROUND AND OBJECTIVES

Since the advent of AIDS, men who have sex with men (MSM) have often been deferred from blood donation. In France, quarantine plasma donation by MSM donors with the same deferral rules as for other donors was introduced in July 2016 and continued up to March 2022. At this time, MSM-specific deferral criteria were lifted for all blood or plasma donation. The donor deferral, as well as rate of infectious markers in plasma donors who would have been otherwise deferred for MSM activity, was evaluated and compared with those of the other donors during the same time period from June 2016 to March 2022.

RESULTS

A total of 8843 MSM donors made 12,250 plasma donation applications. The overall deferral rate was very high (75.2%), mainly due to the absence of apheresis capacity at the donation site. The deferral criteria for sexual risk were present in 12.1% of MSM donors compared with 1.0% in other plasma and blood donors (p < 0.001). Overall, 994 MSM donors made 2880 plasma donations. Of these, one donation was HIV positive (34.7 vs. 0.6/105 donations by other donors, relative risk [RR]: 61.0 [95% confidence interval [CI]: 8.5-437.7]), one was HBV positive (34.7 vs. 4.5/105 , RR: 7.7 [95% CI: 1.1-54.6]) and none were HCV positive (0 vs. 2.4/105 ). Additionally, 21 donations were syphilis positive (729.2 vs. 10.7/105 , RR: 67.9 [95% CI: 44.2-104.4]). A post hoc analysis of eligible MSM donors who were unable to donate plasma due to logistic constraints yielded similar findings.

CONCLUSION

Plasma donation by donors who would have been otherwise deferred for MSM activity was associated with both an increased deferral rate for sexual risk and an increased rate of infectious markers, notably syphilis.

Seropositivity for syphilis among Brazilian blood donors. A retrospective study 2015-2020

INTRODUCTION

Syphilis is a transfusion-transmitted infection and the disease re-emerged in many countries, including Brazil, as a public health risk.

OBJECTIVE

Evaluate the prevalence of positive serology in blood donations rejected by Hemobanco (Curitiba- PR) from January 2015 to December 2020, with special focus in syphilis.

METHODOLOGY

In the studied period, we analyzed the number of blood donations discarded annually for each serological test performed on blood donors' samples, according to gender and donors age.

RESULTS

Within the studied period, 134,741 blood donation were analyzed. 54.5 % of sample were male. Otherwise, it was observed a significant increase in the number of donations by females (P < 0.0001). There was an increase of 437 % in the prevalence of syphilis positive serology made by donors with ≥ 60 years. Besides that, it was noticed a significant increase in donations by aged people throughout these six years (P < 0.0001). The percentage of total blood donation deferred had a significant reduction, although it was observed an increase in the rate of discarded blood bags due to positive serology in the first 4 studied years. It was observed an increase of 20 % in positive syphilis serology.

CONCLUSION

The greatest cause of discard of blood donations changed during the analyzed 5-years; there was an increase in seropositivity donations from donors with ≥ 60 years old. In 2015, Hepatitis B (0.8 %) was the most prevalent and in 2020, syphilis became more prevalent (0.82 %). The medical community should be aware of the rising number of cases of syphilis infection. There is an urgent need to implement actions against the dissemination of this disease.

Effect of storage on survival of infectious Treponema pallidum spiked in whole blood and platelets

BACKGROUND

Blood donations must be tested for evidence of syphilis, a transfusion-transmitted infection. Screening blood for syphilis-related antibodies greatly reduced the risk of transfusion-transmitted syphilis (TTS). It is commonly believed that Treponema pallidum (Tp), the bacterium causing syphilis, does not survive in blood during cold storage-suggested as one reason why no cases of TTS have been recognized in the United States for many years. Some have suggested that routine syphilis screening of blood donations is no longer needed. To address the effect of storage, we investigated the survival of Tp experimentally spiked into blood and platelets stored under conventional conditions.

STUDY DESIGN AND METHODS

We spiked fresh human blood products with high concentrations of Tp and inoculated samples at intervals into rabbits, a sensitive assay detecting infectious Tp. We tested whole blood (WB) stored refrigerated (1-6°C) for 9 days and platelets stored at room temperature for 7 days or refrigerated for 14 days. We assayed sera of the rabbits collected at intervals for seroconversion using two different tests and assessed orchitis. Rabbits were considered infected if one or both serological test results became positive.

RESULTS

Viable Tp survived 7 days in WB and 6 days in platelets stored at both ambient and cold temperatures.

DISCUSSION

Tp at concentrations much higher than those possibly present in an infected blood unit survived in cold blood products longer than previously reported and, thus, storage conditions cannot be relied upon to eliminate T. pallidum from blood or platelets. TTS remains a topic of concern for public health.

Lessons learnt from syphilis-infected blood donors: a timely reminder of missed opportunities

OBJECTIVE

Due to the increased number of syphilis infections diagnosed in the UK and beyond, we reviewed our data on blood donors infected with syphilis in the UK and Ireland between 2016 and 2019.

METHODS

Data were extracted from the surveillance database for all blood donors confirmed positive for syphilis in the UK and Ireland between 2016 and 2019, together with the total number of donations tested during that period. Data on positive cases included gender, age group, reported treatment, symptoms and confirmatory results. All cases were divided into recently acquired within 24 months and past syphilis infection. We also reviewed the information on symptoms characteristic of syphilis reported by blood donors with an untreated syphilis infection during the postdonation discussions.

RESULTS

Screening of 8 246 600 blood donations for treponemal antibodies identified 316 blood donors with confirmed syphilis infection in the UK and Ireland between 2016 and 2019 (1.6 per 100 000 donations). 42% of them (133 of 316) were classed as a recent infection based on their donation testing results, previous donation date and clinical history provided, and they were hence considered potentially infectious. Most of these blood donors (202 of 316, 64%) had not been previously diagnosed or treated for syphilis, although 50 of them reported symptoms consistent with syphilis infection and 19 had been misdiagnosed despite seeking medical help.

CONCLUSIONS

This observational study shows that syphilis infection remains undiagnosed, especially among heterosexual men, and that infectious syphilis is often missed as a differential diagnosis even when donors have presented with genital or oral ulceration, rashes in the genital area and lymphadenopathy. Considering the recent resurgence of syphilis infections in the UK and beyond and our generally expanding sexual networks, it is important to consider syphilis in differential diagnosis even if specific risk factors have not been identified.

Modeling predonation testing strategies in platelet donations - Approach from low throughput apheresis blood center from India

BACKGROUND:

Hospital-based blood centers in India adopt pre-donation testing for transfusion-transmitted infections (TTI) before plateletpheresis donations. However, the WHO emphasizes on TTI tests be performed on samples collected during the donation process. The study objective was to determine whether cost implications by adopting product testing along with predonation testing or only product testing strategy in platelet donation in Indian blood centers.

MATERIALS AND METHODS:

Cross-sectional study on registered plateletpheresis donors, strategy-1 with predonation testing using rapid tests and product testing using chemiluminescence (CLIA) were compared with alternate models: Strategy-2 (predonation test using CLIA and product testing with rapid test) and strategy-3 (product testing). For strategy-1 and 2, donors wait for predonation test to complete or visit blood center twice, while strategy-3 donors donate plateletpheresis immediately. The cost implications of these strategies were compared among registered plateletpheresis donors.

RESULTS:

Out of 560 donors registered with strategy-1, three donors were reactive in predonation tests and six platelet units were discarded at product testing. After modeling, for strategy-2, nine donors would be identified as sero-reactive at pre-donation test only, while in strategy-3, nine units would be discarded in product testing. Only 506 donations were completed in strategy 1 after donor attrition. Recoverable costs was greater for strategy-3 (INR 5,146,500) than strategy-2 (INR 5,120,000) and strategy-1 (INR 5,069,000).

CONCLUSION:

Strategy-3 appears cost-effective but requires regulatory changes in the Indian setting. Testing apheresis procedures using Strategy 2 had greater cost recovery, and also prevents infectious donations and thereby enhances blood safety with the present guidelines.

Prevalence of serologic markers of transfusion and sexually transmitted infections and their correlation with clinical features in a large cohort of Brazilian patients with sickle cell disease

BACKGROUND

Patients with sickle cell disease (SCD) often require red blood cell (RBC) transfusion for clinical complications, so may be exposed to transfusion-transmitted infections (TTIs). The prevalence of markers for human immunodeficiency virus (HIV), hepatitis C virus (HCV) and B (HBV), human T-cell lymphotropic virus (HTLV-1/2), Chagas disease, and syphilis in an SCD cohort in Brazil were studied.

STUDY DESIGN AND METHODS

Clinical history, interview data, blood samples, and medical chart review data were collected during cohort enrollment from November 2013 to May 2015. Serologic markers of infection were assessed. Standard measures of statistical association were calculated, and multivariable models were developed for the most prevalent infections to identify associated factors.

RESULTS

Infection markers were evident in 5.2% (144/2779) of the enrolled cohort. Anti-HCV was detected in 69 (2.5%), syphilis antibodies in 34 (1.2%), anti-HTLV-1/2 in 17 (0.6%), HBV surface antigen in 13 (0.5%), Chagas disease antibodies in 13 (0.5%), and anti-HIV in 8 (0.3%) of participants. Factors associated with increased odds of being anti-HCV reactive were older age, illegal drug use, increasing number of RBCs, more than three pain crises in the previous year, and geographic location. Syphilis was associated with older age, females, and smoking history.

CONCLUSION

HCV infection was more common in older patients who may have received RBCs before testing was performed on donations, suggesting possible historic transfusion transmission. The cohort showed decreasing rates of infections and a reduction in transfusion transmission markers in younger patients compared to historical literature except for syphilis, indicating contemporary reduced risk of TTI.

Challenges of blood transfusions in β-thalassemia

Patients with β-thalassemia major (BTM) require regular blood transfusions, supported by appropriate iron chelation therapy (ICT), throughout their life. β-thalassemia is a global disease that is most highly prevalent in Southeast Asia, Africa, and Mediterranean countries. However, the global distribution of patients with β-thalassemia is changing due to population migration, and Northern European countries now have significant thalassemia populations. Globally, many patients with BTM have limited access to regular and safe blood transfusions. A lack of voluntary nonremunerated blood donors, poor awareness of thalassemia, a lack of national blood policies, and fragmented blood services contribute to a significant gap between the timely supply of, and demand for, safe blood. In many centers, there is inadequate provision of antigen testing, even for common red cell antigens such as CcEe and Kell. Policies to raise awareness and increase the use of red blood cell antigen testing and requesting of compatible blood in transfusion centers are needed to reduce alloimmunization (the development of antibodies to red blood cell antigens), which limits the effectiveness of transfusions and the potential availability of blood. Patients with BTM are also at risk of transfusion-transmitted infections unless appropriate blood screening and safety practices are in place. Hence, many patients are not transfused or are undertransfused, resulting in decreased health and quality-of-life outcomes. Hemovigilance, leukoreduction, and the ability to thoroughly investigate transfusion reactions are often lacking, especially in resource-poor countries. ICT is essential to prevent cardiac failure and other complications due to iron accumulation. Despite the availability of potentially inexpensive oral ICT, a high proportion of patients suffer complications of iron overload and die each year due to a lack of, or inadequate, ICT. Increased awareness, training, and resources are required to improve and standardize adequate blood transfusion services and ICT among the worldwide population of patients with BTM. ICT needs to be available, affordable, and correctly prescribed. Effective, safe, and affordable new treatments that reduce the blood transfusion burden in patients with β-thalassemia remain an unmet need.