Despite implementation of nucleic acid-based screening methods, Hepatitis B virus, or HBV, is still transmitted via transfusion. Occult infection, or OBI, is defined by serologically undetectable hepatitis B surface antigen, despite presence of circulating HBV DNA.
Here is Dr. Jean-Pierre Allain, who led one of these studies: “Rich countries with low prevalence of Hepatitis B Virus and poor countries with high prevalence of the virus are increasingly undertaking considerable financial effort to screen blood with very sensitive but costly genomic detection assays. While the biological efficacy of such screening is quite clear, there is uncertainty regarding the clinical infectious risk of donations from donors with occult Hepatitis B infection.”
Dr. Allain and colleagues retrospectively assessed the infectivity of OBI donors in Europe. They found that 43% of OBI donor recipient pairs had antibodies to HBV core, suggesting prior HBV infection. Additionally, they showed that transfusion-transmitted HBV risk was associated with viral dose and presence of antibodies to hepatitis B surface antigen.
Dr. Allain explains: “We found that OBI-containing blood products can be infectious if at least 100 copies of virus (on average 1000) are present in the transfused product. In addition, we found that the presence of anti-HBs either in the OBI blood (approximately 50% of cases) or vaccine-related or passively received by the recipients significantly decreases infectivity.”
A separate study from Japan assessed transfusion-transmitted HBV from OBI donors and the impact of individual-donation nucleic acid testing, or ID-NAT. The study found that ID-NAT could increase detection of virus in donors with occult or window period infection. ID-NAT of samples suspected in cases of transfusion-transmitted HBV demonstrated that 2% of donations with low levels of anti-core and presence of anti-surface antigen were viremic.
Dr. Celso Bianco and Roger Dodd co-authored an editorial accompanying the two studies. Here is Dr. Bianco: “Most of the residual risk of transmission of HBV is associated with the window period and OBI. Addition of screening for anti-HBs to the screening with anti-Core could help countries with higher prevalence to improve safety without major disruption of the blood supply in the absence of HB-NAT implementation.”
Drs. Bianco and Dodd also noted that while methods to increase sensitivity of nucleic acid testing should be considered, increased assay costs could present barriers to implementation.
We’ll be back with another edition of Transfusion News on August 30th. Thanks for joining us
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