Background: Hepatitis B virus (HBV) causes infection of the liver, with highest prevalence in the Western Pacific and African regions. HBV is known to be transfusion-transmissible (TT). Occult HBV (OBI) is a form of chronic HBV infection typically characterized by undetectable HBV surface antigen and very low levels of HBV DNA, but detectable antibodies to hepatitis B core antigen (anti-HBc). With individual donation nucleic acid amplification testing the risk of HBV TT is negligible, whilst the risk of OBI is significantly decreased with anti-HBc screening. A previous study estimated the deferral of anti-HBc positive donors would lead to the loss of ~2% of Australian donors. The latest calculated residual risk due to OBI infections is within the Australian Red Cross Lifeblood tolerable level of <1 in 1,000,000 components (Seed et al, Vox Sanguinis, 2019).
Aims: To provide a current estimate of the prevalence of anti-HBc in Australian blood donors. Determine the optimal testing strategy to ensure the HBV residual risk remains negligible, considering sufficiency and cost.
Methods: A national serosurvey of 10,000 Australian blood donors is being undertaken; Samples are assayed for anti-HBc II on the Abbott Alinity i instrument, with samples reactive for anti-HBc submitted for external confirmatory testing. We include analysis of the first 1,901 donors, with samples processed in Queensland from July to September 2023. The rate of anti-HBc reactivity and 95% confidence intervals (CI) were calculated. Proportions were compared using chi-squared test, with p< 0.05 considered significant.
Results: Preliminary results from 1,901 donors indicate 27 (1.42%, 95% CI: 0.89 – 1.95%) were anti-HBc initial reactive, with 24 (1.26%, 95% CI: 0.76 – 1.76%) confirmed for anti-HBc. The rate of confirmed anti-HBc was similar in first-time donors (11/958, 1.15%, 95% CI: 0.47 – 1.82%) and repeat donors (13/943, 1.38%, 95% CI: 0.63% - 2.12%) (p = 0.6537).
Conclusion: We show that 1.26% of donors from the state of Queensland, Australia had anti-HBc, which is slightly lower than expected (~2%). The findings will be used to underpin an accurate risk-based assessment of the impact of anti-HBc testing strategies, ensuring the safety of Australia’s blood supply.