Blood Product (Donor) Noninfectious and Infectious Testing and Modification

Blood transfusion begins with safe donor selection and testing. In the United States, the blood supply and transfusion are highly regulated. Blood transfusion safety is multifaceted, whereby each of the elements of the blood safety value chain, spanning donor recruitment and qualification, to collection, blood processing, testing, transfusion practice, and posttransfusion surveillance, must be optimized to minimize risk. Pathogen inactivation is a promising approach to decrease bacterial contamination of platelets, inactivate parasites and viruses, and decrease risks associated with emerging and unidentified pathogens. This article offers an overview of blood donor infectious and noninfectious testing in the United States.

Prevention of transfusion-transmitted infections

Since the 1970s, introduction of serological assays targeting virus-specific antibodies and antigens has been effective in identifying blood donations infected with the classic transfusion-transmitted infectious agents (TTIs; hepatitis B virus [HBV], HIV, human T-cell lymphotropic virus types I and II, hepatitis C virus [HCV]). Subsequently, progressive implementation of nucleic acid-amplification technology (NAT) screening for HIV, HCV, and HBV has reduced the residual risk of infectious-window-period donations, such that per unit risks are <1 in 1 000 000 in the United States, other high-income countries, and in high-incidence regions performing NAT. NAT screening has emerged as the preferred option for detection of newer TTIs including West Nile virus, Zika virus (ZIKV), and Babesia microti Although there is continual need to monitor current risks due to established TTI, ongoing challenges in blood safety relate primarily to surveillance for emerging agents coupled with development of rapid response mechanisms when such agents are identified. Recent progress in development and implementation of pathogen-reduction technologies (PRTs) provide the opportunity for proactive rather than reactive response to blood-safety threats. Risk-based decision-making tools and cost-effectiveness models have proved useful to quantify infectious risks and place new interventions in context. However, as evidenced by the 2015 to 2017 ZIKV pandemic, a level of tolerable risk has yet to be defined in such a way that conflicting factors (eg, theoretical recipient risk, blood availability, cost, and commercial interests) can be reconciled. A unified approach to TTIs is needed, whereby novel tests and PRTs replace, rather than add to, existing interventions, thereby ameliorating cost and logistical burden to blood centers and hospitals.

Emerging Infectious Diseases and Blood Safety: Modeling the Transfusion-Transmission Risk

While the transfusion-transmission (TT) risk associated with the major transfusion-relevant viruses such as HIV is now very low, during the last 20 years there has been a growing awareness of the threat to blood safety from emerging infectious diseases, a number of which are known to be, or are potentially, transfusion transmissible. Two published models for estimating the transfusion-transmission risk from EIDs, referred to as the Biggerstaff-Petersen model and the European Upfront Risk Assessment Tool (EUFRAT), respectively, have been applied to several EIDs in outbreak situations. We describe and compare the methodological principles of both models, highlighting their similarities and differences. We also discuss the appropriateness of comparing results from the two models. Quantitating the TT risk of EIDs can inform decisions about risk mitigation strategies and their cost-effectiveness. Finally, we present a qualitative risk assessment for Zika virus (ZIKV), an EID agent that has caused several outbreaks since 2007. In the latest and largest ever outbreak, several probable cases of transfusion-transmission ZIKV have been reported, indicating that it is transfusion-transmissible and therefore a risk to blood safety. We discuss why quantitative modeling the TT risk of ZIKV is currently problematic.

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During the last 20 years there has been a growing awareness of the threat to blood safety from emerging infectious diseases (EIDs), a number of which are known to be, or are potentially, transfusion-transmissible.

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The transfusion-transmission risk of EID agents can be estimated by risk modeling which can form an important part of risk assessments and inform decisions regarding risk mitigation strategies.

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We describe and compare the methodological principles of two published risk models for estimating the transfusion transmission risk of EIDs.

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We use Zika virus as a case study to demonstrate that reliable risk modeling for EID agents can be problematic due to the uncertainty of the input parameters.