Prevalence ofTreponema pallidumDNA among blood donors with two different serologic tests profiles for syphilis in São Paulo, Brazil

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.

Detection and analysis of blood donors seropositive for syphilis

BACKGROUND

The increasing incidence of syphilis worldwide has called attention to the risk of transmission by transfusion.

AIMS

To determine the prevalence of active syphilis in blood donors and characterise the serological profile of syphilis-positive donors.

METHODS

Samples positive for Treponema pallidum using the chemiluminescent microparticle immunoassay (CMIA) during blood donor screening from 2017 to 2018 were tested by the Venereal Disease Research Laboratory (VDRL) non-treponemal test and for anti-T. pallidum IgM by ELISA (Immunoassay Enzyme test for detection of IgM antibodies). The INNO-LIA Syphilis test (Line Immuno Assay solid test for confirmation antibodies to Treponema pallidum) was performed as a confirmatory test on samples that were positive on ELISA-IgM but negative on VDRL. ELISA-IgM (+) samples were also tested for T. pallidum DNA in sera by real-time polymerase chain reaction (PCR).

RESULTS

Of 248 542 samples screened, 1679 (0.67%) were positive for syphilis by CMIA. Further analysis was performed on 1144 (68.1%) of these samples. Of those tested, 16% were ELISA IgM(+)/VDRL(+), 16.5% were ELISA IgM(-)/VDRL(+), 4.1% were ELISA IgM(+)/VDRL(-), and 63.4% were ELISA IgM (-)/VDRL(-). The INNO-LIA Syphilis test results were 33 (3%) positive, 2 (0.2%) undetermined and 12 (1%) negative. Of the 230 EIA-IgM(+) samples (20.1%), 5 (2.2%) were PCR positive. The prevalence of active syphilis in 2017 and 2018 was 0.1% and 0.07%, respectively, and overall prevalence of serologic markers for syphilis was highest among male, unmarried, 25-34-year-olds with a high school education and who were first-time donors.

CONCLUSION

There is a risk of transfusion-transmitted syphilis in blood banks that exclusively use the VDRL test for donor screening, as is currently the situation in some Brazilian blood centres, as well as in other blood centres around the world.

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

BACKGROUND AND OBJECTIVES

Donor syphilis testing began in the 1940s amidst widespread transfusion-transmitted syphilis (TTS). Since then, the introduction of penicillin, pre-donation screening questionnaires and improved storage conditions have contributed to reducing transmission risk. Consequently, universal testing may no longer be cost-effective. This study analysed alternative options for donor syphilis testing to determine the optimal strategy.

MATERIALS AND METHODS

A model was developed using conservative parameter estimates for factors affecting TTS and 2009-2015 Australian donations to calculate risk outcomes (TTS infections, tertiary syphilis in recipients and transfusion-associated congenital syphilis) and cost-effectiveness of alternative testing strategies. The strategies modelled were as follows: universal testing, targeted-testing of high-risk groups (males ≤50 years old and first-time donors) and no testing.

RESULTS

The estimated risk of TTS is one in 49·5 million transfusions for universal testing, one in 6 million for targeted-testing of males ≤50 years old, one in 4 million for targeted-testing of first-time donors and one in 2·8 million for no testing. For all strategies, the risk of tertiary and congenital syphilis is <1 in 100 million. Universal testing is the least cost-effective strategy with an incremental cost-effectiveness ratio (ICER) estimated at $538·5 million per disability-adjusted life year averted.

CONCLUSION

Universal testing is not required to maintain the risk of TTS within tolerable limits and is estimated to greatly exceed acceptable ICERs for blood safety interventions. However, despite a strong economic and risk-based rationale, given the epidemiology of syphilis in Australia is changing, feedback from critical stakeholders is not currently supportive of reducing testing.

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.