Infectious Disease Testing and Pathogen Reduction in Blood Banking

Keeping the blood supply safe rests on two complementary defences: screening donors and testing each donation for transfusion-transmissible infections, and — increasingly — treating components with pathogen-reduction technologies that inactivate residual microorganisms. Together with donor selection, these measures have made transfusion-transmitted infection rare in well-resourced systems.

Definition

Infectious disease testing and pathogen reduction in blood banking is the layered set of donor-screening, donation-testing, and component-treatment measures used to detect or inactivate transfusion-transmissible pathogens and thereby protect transfusion recipients from infection.

Scope

This topic covers donor selection and deferral, serological and nucleic acid testing for agents such as HIV, hepatitis B and C, and other transfusion-transmissible infections, the concept of the diagnostic window period, and pathogen-reduction (pathogen-inactivation) methods applied to plasma and platelets. It is a reference account of how blood safety is achieved, not operational laboratory guidance.

Core questions

• How are blood donors selected and donations tested for transmissible infections?
• What is the window period, and how does nucleic acid testing shorten it?
• Which agents are routinely screened, and how is emerging-pathogen risk addressed?
• What are pathogen-reduction technologies and which components can they treat?

Key concepts

• Donor selection and deferral
• Serological screening
• Nucleic acid testing
• Window period
• Residual risk
• Pathogen reduction (pathogen inactivation)

Mechanisms

Blood safety is built in layers. Donor questionnaires and deferral exclude higher-risk donations before collection. Each donation is then tested serologically for markers of infection and, for key viruses, by nucleic acid testing, which detects viral genetic material before antibodies appear and so shortens the window period during which an infected donation could escape detection (stramer-2004). Because no test detects the very earliest infection, a small residual risk remains, which haemovigilance monitors (vamvakas-2009). Surveillance also tracks emerging or under-recognised agents such as hepatitis E, where testing programmes quantify and limit transmission (harritshoj-2016). Pathogen-reduction technologies add a further layer by chemically or photochemically damaging the nucleic acids of any residual pathogens in plasma and platelets, broadening protection against agents not specifically screened for; randomised trials have evaluated the clinical effects of pathogen-reduced platelets (rebulla-2020).

Clinical relevance

Understanding the layered defences of donor screening, donation testing, and pathogen reduction explains why transfusion-transmitted infection is now rare and how residual risk is managed. This entry describes blood-safety practice and evidence; it is not laboratory protocol or guidance for any individual transfusion decision.

Epidemiology

Successive introduction of serological assays and then nucleic acid testing has driven the residual risk of HIV and hepatitis C transmission to very low levels in well-resourced systems, as documented in donor cohorts where nucleic acid testing identified antibody-negative window-period infections (stramer-2004). Surveillance of newer concerns such as hepatitis E shows low but measurable transmission, informing decisions about additional screening (harritshoj-2016).

History

Donor screening began with serological tests for syphilis and hepatitis B, expanded after the emergence of HIV and the identification of hepatitis C, and was transformed by the introduction of nucleic acid testing around the turn of the century, which substantially shortened the detection window. Pathogen-reduction technologies, developed more recently, extend protection beyond the agents that are individually screened (stramer-2004, rebulla-2020).

Debates

Should pathogen reduction replace or supplement targeted testing?

Pathogen-reduction technologies broaden protection against unscreened and emerging agents, but their cost, effects on component quality, and the strength of clinical outcome evidence are debated, so they are generally adopted alongside rather than instead of established testing.

Seminal works

• stramer-2004
• rebulla-2020
• vamvakas-2009

Frequently asked questions

What is the window period in blood-donor testing?

It is the interval after infection during which a donor is infectious but tests cannot yet detect the agent; nucleic acid testing shortens this period for viruses such as HIV and hepatitis C by detecting viral genetic material before antibodies appear.

How does pathogen reduction differ from infectious-disease testing?

Testing screens each donation for specific known agents, whereas pathogen reduction treats the component itself to inactivate a broad range of residual pathogens, including some that are not individually screened for; the two approaches are complementary.