Hepatitis B infections among blood donors in England between 2009 and 2018: Is an occult hepatitis B infection a risk for blood safety?

Low rate of hepatitis Delta virus co-infection in first-time blood donors diagnosed with chronic hepatitis B virus infection in the Netherlands

BACKGROUND

Hepatitis Delta virus (HDV) requires co-infection with hepatitis B virus (HBV) and increases the risk of hepatitis-related morbidity and mortality compared to HBV mono-infection. HBV/HDV co-infected patients will likely benefit from new HDV antiviral drugs, but reliable estimates of co-infection rates are lacking due to limited HDV testing of HBV-infected patients.

STUDY DESIGN AND METHODS

First-time blood and bone tissue donors in the Netherlands (2006-2023) with a newly diagnosed chronic HBV infection were retrospectively tested for HDV antibodies, and for HDV RNA if HDV antibodies were detected. HBV genotyping using phylogenetic analysis was performed to determine the most likely origin of HBV infection.

RESULTS

HBV-DNA was detected in 254/758.081 (0.034%) first-time donors in the Netherlands. HBsAg-positive first-time donors had a median age of 43 years (IQR: 33-52), were predominantly male (67%), mostly first- or second-generation migrants (76%) and HBV (sub)genotype strongly correlated with the country of birth. HDV testing was performed for 200 first-time donors with chronic (HBsAg-positive) HBV infection: 5 donors (2.5%) had HDV antibodies, and 1 donor (0.5%) also had detectable HDV RNA. None of the 17 donors with occult (HBsAg-negative) HBV infection had experienced HDV infection.

DISCUSSION

Chronic HBV/HDV co-infection in first-time donors in the Netherlands is extremely rare, affecting 0.00013% of all first-time donors, and only 0.5% of HBsAg-positive first-time donors consisting predominantly of migrants from high(er) HDV-endemic countries. Despite low HBV/HDV co-infection rates, a one-time HDV reflex testing strategy for HBsAg-positive patients remains essential to identify patients and to initiate antiviral treatment if needed to reduce the risk of serious liver disease.

Occult hepatitis B virus infection: risk for a blood supply, but how about individuals' health?

The implementation of effective blood donation screening for hepatitis B virus (HBV) anti-core antibodies with highly sensitive molecular HBV DNA detection in low-endemic countries like the United Kingdom has improved blood safety. However, the linkage to care and management for blood donors with occult HBV infection (OBI) is a complex dilemma involving virological, clinical, methodological, and social issues. Limited evidence suggests that OBI may accelerate the progression of liver disease and cancer. The need for a specialist referral for donors identified with OBI carries mixed opinions from blood establishments, hepatologists, and public health. Following extensive multidisciplinary discussions, experts agree upon a need for clear messaging for donors and to consider the oncogenic implications of OBI. Proposals for future studies are identified, and the applicability of the recommendations in low-resource, high-endemic regions is considered, as well as the inclusion of OBI in global hepatitis elimination targets.

Prevalence and Transfusion Risks of Occult Hepatitis B Infection Among HBcAb-Positive Blood Donors in a High-Endemic Region

Background: Hepatitis B virus (HBV) remains a significant global health concern, particularly in sub-Saharan Africa, where endemicity is high. Occult hepatitis B infection (OBI) presents a unique challenge to transfusion safety, as HBV DNA may persist in HBsAg-negative individuals. This study examines the prevalence of HBcAb positivity among blood donors at Usmanu Danfodiyo University Teaching Hospital (UDUTH), Sokoto, and assesses the risk of HBV transmission. Methods: A cross-sectional study was conducted among 200 blood donors. Samples were screened for HBsAg and HBV serological markers using a rapid assay and ELISA. HBcAb-positive samples were analyzed for HBV DNA using real-time polymerase chain reaction (qRT-PCR). Viral loads were quantified, and socio-demographic characteristics were recorded. Results: HBcAb was detected in 57 (28.5%) of the 200 donors. The most common serological pattern among donors was HBsAg-negative and HBcAb-negative (69%). Among these HBcAb-positive donors, HBV DNA was detected in three cases (1.5%), with viral loads of 753.1, 2.193 × 104, and 4.538 × 104 IU/mL. The presence of HBV DNA in these donors confirms the risk of OBI transmission through transfusion. Socio-demographic analysis revealed that 48.5% of donors were aged 26-35 years, 23.5% were aged 18-25 years, 23% were aged 36-42 years, and 2.5% were either 43-50 or above 50 years of age, of which 99.5% were male. These findings highlight a significant prevalence of HBcAb positivity and OBI, aligning with studies in similar high-endemic settings. Conclusions: HBcAb positivity and OBI represent significant transfusion risks in endemic regions. The presence of HBV DNA in 1.5% of HBcAb-positive donors in the study population highlights the limitations of HBsAg-based screening. Incorporating nucleic acid testing (NAT) into routine blood donor screening protocols is critical to enhancing transfusion safety. Further research is needed to evaluate the feasibility and cost-effectiveness of such interventions in resource-limited settings.

Prevalence and molecular characteristics of occult hepatitis B virus infection among blood donors in Huzhou City, eastern China

Occult hepatitis B virus (HBV) infection (OBI) is a significant challenge for HBV prevention and control. We investigated the prevalence and surface (S) gene mutations of OBI among blood donors in Huzhou City, eastern China. The hepatitis B surface antigen (HBsAg) was routinely screened among 44,256 blood donors. HBV-DNA was detected using the Roche cobas®system. Serum samples that were HBsAg negative and HBV-DNA positive were selected, and the HBV S gene was amplified and sequenced. HBV genotype and S gene mutations were analyzed. The OBI rate in these blood donors was 0.070 % (31/44,256). Among the blood donors with OBI, only two cases (2/31, 6.5 %) were anti-HBc negative. The S gene sequences of 28 samples were successfully obtained, and we found that HBV genotype C (21/28, 70 %) was predominant among blood donors with OBI. Most S gene mutations were associated with OBI, and the high frequency mutations included N40S, G44E, Q51R/P, T113A/S,T118K/M, P120Q/S/T, and Y161F/S. Notably, amino acid substitutions at some sites differed from those reported previously, such as Y72F, G102V, P127L, Q129P, and S143T. Additionally, six novel mutations (S31I/N/R, P46L, S58C, C76Y, Y200F/C, and I208T) that may be associated with OBI were found. OBI was detected in a certain proportion of blood donors in Huzhou City. S gene mutations play an important role in OBI development. Further research is required to explore the functions of novel S gene mutants in OBI pathogenesis. The findings of this study may provide important insights to prevent HBV transmission through blood transfusions.

International review of blood donation screening for anti-HBc and occult hepatitis B virus infection

BACKGROUND

Hepatitis B core antibody (anti-HBc) screening has been implemented in many blood establishments to help prevent transmission of hepatitis B virus (HBV), including from donors with occult HBV infection (OBI). We review HBV screening algorithms across blood establishments globally and their potential effectiveness in reducing transmission risk.

MATERIALS AND METHODS

A questionnaire on HBV screening and follow-up strategies was distributed to members of the International Society of Blood Transfusion working party on transfusion-transmitted infectious diseases. Screening data from 2022 were assimilated and analyzed.

RESULTS

A total of 30 unique responses were received from 25 countries. Sixteen respondents screened all donations for anti-HBc, with 14 also screening all donations for HBV DNA. Anti-HBc prevalence was 0.42% in all blood donors and 1.19% in new donors in low-endemic countries; however, only 44% of respondents performed additional anti-HBc testing to exclude false reactivity. 0.68% of anti-HBc positive, HBsAg-negative donors had detectable HBV DNA. Ten respondents did universal HBV DNA screening without anti-HBc, whereas four respondents did not screen for either. Deferral strategies for anti-HBc positive donors were highly variable. One transfusion-transmission from an anti-HBc negative donor was reported.

DISCUSSION

Anti-HBc screening identifies donors with OBI but also results in the unnecessary deferral of a significant number of donors with resolved HBV infection and donors with false-reactive anti-HBc results. Whilst confirmation of anti-HBc results could be improved to reduce donor deferral, transmission risks associated with anti-HBc negative OBI donors must be considered. In high-endemic areas, highly sensitive HBV DNA testing is required to identify infectious donors.

Implementing pathogen reduction technology while discontinuing blood donor deferral criteria for sexual risk behaviors: A simulation study

BACKGROUND

Combining pathogen reduction technology (PRT) with blood screening may alleviate concerns over the risk of transfusion-transmitted infections (TTI) and support changes in blood donor selection to potentially increase blood availability. This study aimed to estimate the residual risk of human immunodeficiency virus (HIV), hepatitis B virus (HBV), and hepatitis C virus (HCV) transfusion-transmission in Canada after implementing PRT, while eliminating deferrals for sexual risk behaviors.

STUDY DESIGN AND METHODS

A probabilistic approach that combined Bayesian networks with Monte Carlo simulations was used to estimate the risk of transfusing HIV-, HBV-, or HCV-contaminated blood components. Different scenarios were considered to compare the current residual risk after PRT implementation, with and without donor deferral criteria for sexual risk behaviors. Donor profiles and blood component outcomes were simulated based on a literature review including the prevalence and incidence of HIV, HBV, and HCV in the Canadian blood donor population; the use of current blood screening assays; and HIV, HBV, and HCV blood donor viral loads.

RESULTS

In the universal PRT scenario (i.e., with PRT/without deferral criteria), the estimated risks of HIV, HBV, and HCV transmission were significantly lower than those in the currently observed scenario (i.e., without PRT/with deferral criteria).

CONCLUSIONS

This risk model suggests that PRT for platelets and plasma (and eventually for RBCs when available) significantly reduces the residual risks of HIV, HBV and HCV transfusion-transmission and could enable the removal of blood donor deferral criteria for sexual risk behaviors.

Blood donation screening for hepatitis B virus core antibodies: The importance of confirmatory testing and initial implication for rare blood donor groups

BACKGROUND AND OBJECTIVES

Exclusion of blood donors with hepatitis B virus (HBV) core antibodies (anti-HBc) prevents transfusion-transmitted HBV infection but can lead to significant donor loss. As isolated anti-HBc positivity does not always indicate true past HBV infection, we have investigated the effectiveness of confirmatory anti-HBc testing and the representation of rare blood groups in anti-HBc-positive donors.

MATERIALS AND METHODS

Three hundred ninety-seven HBV surface antigen-negative and anti-HBc initially reactive blood donor samples were tested by five different anti-HBc assays.

RESULTS

Eighty percentage of samples reactive in Architect anti-HBc assay were positive by the Murex assay and anti-HBc neutralization. Eleven out of 397 samples showed discordant results in supplementary testing from the Murex confirmatory test result, and five remained undetermined following extensive serological testing. Thirty-eight percentage of anti-HBc-positive donors identified as minority ethnic groups compared with 11% representation in anti-HBc-negative donors (p < 0.0001); the frequency of the Ro blood group in anti-HBc-positive donors was 18 times higher in non-white ethnic groups.

CONCLUSION

Using two anti-HBc assays effectively enabled the identification of HBV-exposed and potentially infectious donors, their deferral and potential clinical follow-up. However, the exclusion of confirmed anti-HBc-positive donors will still impact the supply of rare blood such as Ro.

Biomarkers of transfusion transmitted occult hepatitis B virus infection: Where are we and what next?

Blood transfusion is a vital procedure, where transfusion-transmitted infection of hepatitis B virus (HBV) remains an important issue, especially from blood donors with occult hepatitis B virus infection (OBI). Occult hepatitis B virus infection is a complex entity to detect using surrogate blood biomarkers for intrahepatic viral transcriptional activity, requiring a continually refined battery of tests utilised for screening. This review aims to critically evaluate the latest advances in the current blood biomarkers to guide the identification of OBI donors and discuss novel HBV markers that could be introduced in future diagnostic practice. Challenges in detecting low HBV surface antigen levels, mutants, and complexes necessitate ultrasensitive multivalent dissociation assays, whilst HBV DNA testing requires improved sensitivity but worsens inaccessibility. Anti-core antibody assays defer almost all potentially infectious donations but have low specificity, and titres of anti-surface antibodies that prevent infectivity are poorly defined with suboptimal sensitivity. The challenges associated with these traditional blood HBV markers create an urgent need for alternative biomarkers that would help us better understand the OBI. Emerging viral biomarkers, such as pre-genomic RNA and HBV core-related antigen, immunological HBV biomarkers of T-cell reactivity and cytokine levels, and host biomarkers of microRNA and human leucocyte antigen molecules, present potential advances to gauge intrahepatic activity more accurately. Further studies on these markers may uncover an optimal diagnostic algorithm for OBI using quantification of various novel and traditional blood HBV markers. Addressing critical knowledge gaps identified in this review would decrease the residual risk of transfusion-transmitted HBV infection without compromising the sustainability of blood supplies.

Prevalence of Hepatitis B in Canadian First-Time Blood Donors: Association with Social Determinants of Health

Hepatitis B is transmitted sexually, by blood contact, and vertically from mother to child. Chronic hepatitis B is often seen in immigrants from higher-prevalence countries and their Canadian-born children. We assessed the relationship between hepatitis B and social determinants of health. Included were 1,539,869 first-time Canadian blood donors from April 2005 to December 2022. All donations were tested for hepatitis B markers. Logistic regression was fit with chronic hepatitis B as the dependent variable and age, sex, year, and ethnocultural composition and material deprivation quintiles as independent variables. Chronic hepatitis B prevalence was 47.5/100,000 (95% CI 41.5-53.5, years 2017-2022). Chronic hepatitis B prevalence was elevated in males, older age groups, and those living in more materially deprived and higher ethnocultural neighbourhoods. Of 212,518 donors from 2020 to 2022 with race/ethnicity data, chronic hepatitis B prevalence was highest in East Asians. The findings are consistent with infections in immigrants, acquired in their country of origin, in their Canadian-born children and in those with other risks. As blood donors are a low-risk population unaware of their infection and unlikely to seek testing, our results highlight the ongoing public health challenges of diagnosing chronic hepatitis B and treating it when appropriate.

Changes and gaps of global and regional disease burden of hepatitis B infection in children younger than 5 years old between 2015 and 2019: A real-world data review

Hepatitis B virus (HBV) infection has been declared an ongoing health threat, especially infections among children. We compared and updated the disease burden of HBV infection and the effectiveness of vaccination among children younger than 5 years to offer indications for hepatitis B prevention across the world. The country-level data on the prevalence of hepatitis B surface antigen (HBsAg), the coverages of hepatitis B vaccine birth-dose (HepB-BD), three-dose series (HepB3), income level, population density/size, and human development index were collected from open access databases including WHO, UNICEF, and World Bank. Comparison of the prevalence of HBsAg under 5 years old between 2015 and 2019 based on vaccination coverages was conducted by the gamma generalized linear mixed model. Globally, more than 6.3 million HBV infections were estimated in children under 5 years in 2019, compared to 10.1 million in 2015 within the 179 countries involved. The pooled average prevalence of HBsAg among children younger than 5 years decreased from 1.4% (95% confidence interval [CI]: 1.1-1.8) to 0.9% (95% CI: 0.7-1.2). The rate difference or rate ratio was -0.5% (95% CI: -0.6% to -0.3%) or 0.51(95% CI: 0.44-0.58), respectively. Countries from the African region or with lower income/population density/human development indexes bore the most significant disease burden of hepatitis B. Higher coverages of hepatitis B vaccine birth-dose or primary series correlated with significant HBsAg prevalence decreases and much-decreased ratio, independently. Hepatitis B prevention among children under 5 years has significantly been achieved while remaining the most life-threatening disease burden, unequally distributed worldwide. The hepatitis B vaccination should be prioritized for all newborns, especially in those resource-constrained countries or regions.

Novel Assays to Solve the Clinical and Scientific Challenges of Chronic Hepatitis B

Chronic infection with Hepatitis B is a common, incurable, and deadly infection. Despite inexpensive laboratory tests for diagnosis and management that have been established for decades, the worldwide rate of diagnosis is only ∼10%, and ∼5% of people are under treatment. Novel assays have been developed to improve linkage to care by providing more flexible approaches to determine a patient's health status. Other assays have been established to better investigate intrahepatic host-virus interactions to support clinical trials for cure research. This review outlines the clinical and scientific challenges still to be solved and the upcoming methods used to address them.

Ultrasensitive PCR system for HBV DNA detection: Risk stratification for occult hepatitis B virus infection in English blood donors

Occult hepatitis B (HBV) infection (OBI), characterized by low viral loads, accounts for much of the risk of HBV transfusion-transmitted infection. With anticore antibodies (anti-HBc) screening introduced in England, the imperative to identify OBI donors has increased. We aimed to develop an ultra-sensitive PCR system and investigate risk factors for HBV DNA presence in blood donations. Seven extraction methods and three PCR assays were compared. The optimal system was sought to determine HBV DNA presence in anti-HBc-positive donations. Predictors of DNA positivity were subsequently investigated. Extraction from 5 mL of plasma increased sample representation and resulted in HBV DNA detection in low viral load samples (~0.5 IU/mL). Screening of 487 763 donations in 2022 identified two OBI donors and 2042 anti-HBc-positive donors, 412 of the latter with anti-HBs < 100 mIU/mL. Testing of 134 anti-HBc-positive donations utilizing the 5 mL extraction method identified two further HBV DNA-positive donations. Higher anti-HBc titer and anti-HBs negativity were significant predictors of DNA detectability in anti-HBc-positive donations. An ultrasensitive PCR assay identified potentially infectious donations increasing HBV DNA detection in anti-HBc-positive donors from 0.5% to 1.9%. Anti-HBc titers may further complement the risk stratification for DNA positivity in anti-HBc screening and minimize unnecessary donor deferral.

Occult hepatitis B in Iranian blood donors, an overview of the challenges: A narrative review

Background

Occult hepatitis B infection (OBI) is a transfusion-transmitted infection. Although, screening the hepatitis B virus among blood donors can play an important role in increasing the health of blood products, OBI screening in blood transfusion centers is still a challenge. This review study aimed to appraise the challenges of OBI screening and its associated do's and don'ts in blood transfusion centers.

Methods

In this review study, a search was conducted on the electronic databases of PubMed, Web of Science, Scopus, Ovid, Irandoc, and Magiran from January 1996 to December 2020. Also, cross-sectional studies that determined the prevalence of OBI or anti-HBc were included in the study. In addition, studies with incomplete data on the prevalence of OBI were excluded.

Results

The prevalence of OBI varies among Iranian blood donors. The rates reported by blood transfusion centers of Mashhad, Ahvaz, and Tehran were 0%, and Isfahan, Shiraz, and Kerman were 0.9%, 0.08%, and 2.36%, respectively. In areas with high prevalence of hepatitis B virus, OBI screening only by anti-HBc test led to the exemption of blood donors from donating blood. Avoiding OBI screening also effected the risk of virus transmission to blood recipients. Plasma products had a higher risk (85%) of virus transmission.

Conclusions

Determining an appropriate screening strategy based on prevalence status, the cost-effectiveness of screening tests, and the policies of each blood transfusion center is essential.

Challenges for the maintaining the microbiological safety of the UK blood supply

The supply of blood, blood products and components in the UK, as elsewhere, is safe, although there is no cause for complacency. Use of blood, blood products and components is not without risk of morbidity and mortality. Transfusion-transmitted infections (TTIs) continue to occur and may severely affect the health and welfare of recipients. As indicated by recent and current inquiries, public interest in these TTIs is huge. The risk of TTI can be mitigated but not abolished. Measures to reduce risk include screening of donors, testing of donations and, where appropriate, treatment of donations. The introduction of newer screening tests might identify some infectious donations but come at a cost, which could exceed a justifiable limit. Thus, the recognition, detection, reporting and investigation of cases of possible TTIs need to be improved. Recipients of blood should understand that, although transfusion in the UK is safe, it is not free of risk and so should be provided with full information so that properly informed consent can be given.

Healthcare-associated hepatitis B and C transmission to patients in the EU/EEA and UK: a systematic review of reported outbreaks between 2006 and 2021

Healthcare-associated transmission was the second most common hepatitis B (HBV) and hepatitis C (HCV) transmission route according to 2006-2012 European surveillance data, but data quality and completeness issues hinder comprehensive characterisation of this important issue. We carried out a systematic review of published literature on healthcare-associated transmission of HBV or HCV in European Union (EU) and European Economic Area (EEA) countries and the United Kingdom to complement surveillance data and identify higher-risk settings. We searched the PubMed and Embase databases and grey literature over the period January 2006 to September 2021, for publications reporting transmission events after 2000 in the EU/EEA and UK related to a healthcare setting or procedure. We collected data on the country, number of patients, setting type and route of transmission. In 65 publications from 16 countries, 43 HBV and 48 HCV events were identified resulting in 442 newly infected patients. Most events were reported from Italy (7 HBV and 12 HCV), Germany (8 HBV and 5 HCV) and the United Kingdom (8 HBV and 5 HCV). The number of patients infected from a single source within an event ranged from 1 to 53. Five large outbreaks of over 20 cases were identified, including two in Poland and one each in Belgium, Hungary and Slovakia. The majority of transmission events occurred through blood transfusions or in dialysis units. However, there were a number of outbreaks in seemingly low risk settings such as CT/MRI scanning units. A failure to adequately follow infection prevention control (IPC) precautions was reported in 30% of included studies. Healthcare-associated transmission of hepatitis B and C continues to occur in a range of community and hospital settings across EU/EEA countries and often results in large outbreaks, although the true extent of the situation cannot be fully determined due to under-reporting. Strict IPC precautions should be implemented across all healthcare settings and regularly audited, and surveillance systems strengthened and standardised to allow for comprehensive and consistent reporting of nosocomial transmission of hepatitis across the EU.

Evolution of Blood Safety in Switzerland over the Last 25 Years for HIV, HCV, HBV and Treponema pallidum

During the last few decades, efforts to increase the safety of blood and blood products have mainly focused on preventing the viral infections HCV, HIV, HBV and Treponema pallidum. The evolution of these approaches and the achieved increase in safety is shown for the last 25 years in Switzerland. In detail, the prevalences and incidences of the infection disease and the theoretical estimated residual risks (RR) of these blood-borne infections are presented. Prevalences, incidences and, in particular, the RR have decreased considerably over the last 25 years. This was achieved primarily by the adoption of strict criteria for the selection of blood donors, refined questionnaires, the introduction of increasingly sensitive serological screening tests and the implementation of nucleic acid testing (NAT) for these blood-borne pathogens. These NAT assays have significantly shortened the window period between infection and the first detection of the infectious agent in the blood of an infected individual. A form of "real life" comparison or confirmation is provided by the reported lookback procedures (LBP) and the haemovigilance data of the Swiss competent authority, Swissmedic. These data are in agreement, and thus support the very low prevalences, incidences and RR.

Insights on 21 Years of HBV Surveillance in Blood Donors in France

Hepatitis B virus (HBV) infection is the most frequent viral infection found in blood donors (BDs) in France. We analyzed the epidemiological and sero-molecular data on HBV infection gathered over the past two decades by the French haemovigilance surveillance network, blood screening laboratories, and the national reference center for transfusion infectious risks (NRC). Between 2000 and 2020, 6149 of the 58,160,984 donations (1.06/10,000) tested HBV positive, 98% of them from first-time blood donors (FTBDs). In addition, 2212 (0.0071%) of the 30,977,753 donations screened for HBV DNA tested DNA positive, of which 25 (1.1%) were positive only for this marker. HBV prevalence decreased by 2.8-fold and the residual risk for transfusion-transmitted HBV infection decreased 13-fold and was divided by 13. The major risk factor for HBV infection was the origin of donors (endemic country, 66.5%), followed by parenteral exposure (10.7%). In the whole HBV-positive BD population, genotype D was predominant (41.8%), followed by genotypes A (26.2%) and E (20.4%), reflecting the geographical origin of donors. The low and decreasing prevalence and incidence of HBV infection in French BDs, coupled with a screening strategy using three HBV markers (HBsAg, anti-HBc and DNA), ensures a high level of blood safety, further reinforced by the implementation of pathogen-reduction measures.

Prevalence of occult hepatitis B virus infection in adults: a systematic review and meta-analysis

Background

Despite growing concerns about transmissibility and clinical impact, occult hepatitis B virus (HBV) infection has received little attention in the hepatitis elimination agenda. We aimed to estimate the prevalence of occult HBV infection at a global and regional scale and in specific populations.

Methods

For this systematic review and meta-analysis, we searched the MEDLINE, Embase, Global Health, and Web of Science databases for articles published in any language between Jan 1, 2010, and Aug 14, 2019. We included original articles and conference abstracts of any study design that reported the proportion of HBsAg-negative adults (aged ≥18 years) who are positive for HBV DNA (ie, people with occult HBV infection). The prevalence of occult HBV infection was pooled, using the DerSimonian-Laird random-effects model, in the general population and specific groups defined by the type of study participants (blood donors; other low-risk populations; high-risk populations; and people with advanced chronic liver disease), and stratified by HBV endemicity in each country. We also assessed the performance of anti-HBc as an alternative biomarker to detect occult HBV infection. The study was registered with PROSPERO, CRD42019115490.

Findings

305 of 3962 articles were eligible, allowing a meta-analysis of 140 521 993 individuals tested for HBV DNA. Overall, only two studies evaluated occult HBV infection in the general population, precluding unbiased global and regional estimates of occult HBV infection prevalence. In blood donors, occult HBV infection prevalence mirrored HBV endemicity: 0·06% (95% CI 0·00–0·26) in low-endemicity countries, 0·12% (0·04–0·23) in intermediate-endemicity countries, and 0·98% (0·44–1·72), in high-endemicity countries (p=0·0012). In high-risk groups, occult HBV infection prevalence was substantial, irrespective of endemicity: 5·5% (95% CI 2·9–8·7) in low-endemicity countries, 5·2% (2·5–8·6) in intermediate-endemicity countries, and 12·0% (3·4–24·7) in high-endemicity countries. The pooled sensitivity of anti-HBc to identify occult HBV infection was 77% (95% CI 62–88) and its specificity was 76% (68–83).

Interpretation

A substantial proportion of people carry occult HBV infection, especially among high-risk groups across the globe and people living in highly endemic countries. Occult HBV infection should be part of the global viral hepatitis elimination strategy.

Funding

None.

Prevalence of Occult Hepatitis B Virus Infection in Blood Donors with Negative ID-NAT in Switzerland

Introduction

Screening of hepatitis B surface antigen (HBsAg) and individual-donation nucleic acid amplification testing (ID-NAT) of blood donors have become standard to detect hepatitis B virus (HBV) infection. However, there is still a residual risk of HBV transmission by blood components of donors suffering from occult HBV infection (OBI). Therefore, many countries implemented universal testing of anti-HBV core antigen (anti-HBc) antibodies in order to increase blood safety. In Switzerland, anti-HBc testing is not part of the routine blood donor-screening repertoire. Therefore, we sought to assess prevalence of donors with OBI in a Swiss blood donor collective.

Methods

Blood donations were prospectively investigated for the presence of anti-HBc antibodies during two time periods (I: all donors, March 2017; II: first-time donors only, April 2017 until February 2018). Anti-HBc-positive findings were confirmed by an anti-HBc neutralization test. Discarded plasma samples of anti-HBc-confirmed positive donors were ultracentrifuged and subsequently retested by regular HBV-ID-NAT to search for traces of HBV.

Results

During time period I, 78 (1.6%) individuals out of 4,923 donors were confirmed anti-HBc-positive. Sixty-nine (88%) anti-HBc-positive samples were available and processed by ultracentrifugation followed by repeat HBV-ID-NAT. Four samples (5.8%) were found positive for HBV DNA. Sixty-five (94.2%) samples remained HBV NAT-negative upon ultracentrifugation. During time period II, 56 (0.9%) donor samples out of 6,509 exhibited anti-HBc-confirmed positive. Fifty-five (98%) samples could be reassessed by HBV-ID-NAT upon ultracentrifugation. Three (5.5%) samples contained HBV DNA and 52 (94.5%) samples remained HBV NAT-negative.

Conclusion

Overall, we detected 7 viremic OBI carriers among 11,432 blood donors, which tested negative for HBV by standard HBV-ID-NAT and HBsAg screening. In contrast, OBI carriers showed positive anti-HBc findings which could be confirmed in 83.8% of the cases. Thus, OBI might be missed by the current HBV screening process of Swiss blood donors. We suggest to review current HBV screening algorithm. Extended donor screening by anti-HBc testing may unmask OBI carriers and contribute to blood safety for the recipient of blood products.

Estimating the epidemiology of chronic Hepatitis B Virus (HBV) infection in the UK: what do we know and what are we missing?

Background: HBV is the leading global cause of cirrhosis and primary liver cancer. However, the UK HBV population has not been well characterised, and estimates of UK HBV prevalence and/or incidence vary widely between sources. We aimed to i) extract and summarise existing national HBV prevalence estimates, ii) add a new estimate based on primary care data, and; iii) critique data sources from which estimates were derived. Methods: We undertook a narrative review, searching for national estimates of CHB case numbers in the UK (incorporating incidence, prevalence and/or test positivity data) across a range of overlapping sources, including governmental body reports, publications from independent bodies (including medical charities and non-governmental organisations) and articles in peer-reviewed scientific journals.  An alternative proxy for population prevalence was obtained via the UK antenatal screening programme which achieves over 95% coverage of pregnant women. We also searched for diagnoses of HBV in the QResearch primary care database based on laboratory tests and standardised coding. Results: We identified six CHB case number estimates, of which three reported information concerning population subgroups, including number of infected individuals across age, sex and ethnicity categories. Estimates among sources reporting prevalence varied from 0.27% to 0.73%, congruent with an estimated antenatal CHB prevalence of <0.5%. Our estimate, based on QResearch data, suggests a population prevalence of ~0.05%, reflecting a substantial underestimation based on primary care records. Discussion: Estimates varied by sources of error, bias and missingness, data linkage, and "blind spots" in HBV diagnoses testing/registration. The UK HBV burden is likely to be concentrated in vulnerable populations who may not be well represented in existing datasets including those experiencing socioeconomic deprivation and/or homelessness, ethnic minorities and people born in high-prevalence countries. This could lead to under- or over-estimation of population prevalence estimation. Multi-agency collaboration is required to fill evidence gaps.

Residual risk of transfusion-transmitted hepatitis B virus (TT-HBV) infection by NAT-screened blood components: A review of observed versus modeled infectivity from donors with window period and occult HBV infections

BACKGROUND

The residual transfusion-transmitted hepatitis B virus (TT-HBV) risk with different testing strategies depends on the sensitivity of screening assays, the prevalence of hepatitis B surface antigen (HBsAg) compared to HBV-DNA in window period (WP) and occult HBV infections (OBIs), and infectivity of blood in these infection stages. We compared modeled WP and OBI transmission risk in a multiregional individual donation nucleic acid amplification technology (ID-NAT) screening study with observed TT-HBV infection rates in several lookback studies.

STUDY DESIGN AND METHODS

The WP and OBI risk was estimated from ID-NAT screening data in six geographic regions. The 50% infectious dose (ID₅₀ ), a key factor in the applied risk models, was assumed to be 100-fold higher in OBI than in WP blood. The relative proportion of WP and OBI TT-risk was estimated for different screening scenarios and expressed as a percentage of the ID-NAT yield rate to allow for comparison with observed TT-rates in lookback studies.

RESULTS

Despite sevenfold to eightfold higher HBV ID-NAT yield rates in OBI than WP in South-East Asia and Europe, our models predicted that 40 (26-55)% of total residual TT-HBV risk was due to OBI, comparable to 37% observed in a Japanese hemovigilance study. Modeled TT-OBI risk was approximately 10-fold higher than observed rates of 2%-8% in five lookback studies but comparable to one other study (36%).

CONCLUSION

Although the observed TT-OBI rate was generally lower than the modeled risk, the relative risk of WP versus OBI transmission was not incompatible with the observational infectivity data. This supports the validity of our assumptions in the infectivity-based models for estimating worst-case residual risk with different testing scenarios.