In Focus
Pathogen inactivation or bacterial screening
Advantages and disadvantages
Bacterial contamination remains one of the most important infectious risks associated with platelet transfusion.
Two major strategies have emerged: Pathogen Inactivation (PI) and bacterial screening (BS). The purpose of this comparison is not to determine which technology is universally superior. Rather, the relevant question for individual blood services is which strategy provides the best fit for their organisation. Both approaches have demonstrated an excellent ability to reduce transfusion transmission of bacteria in platelets (Table 1). The comparison focused on two systems with extensive surveillance data: the INTERCEPT PI system (Cerus corporation) and the BacT/ALERT culture-based BS system (bioMérieux).
Table 1. Comparison of Transfusion Transmitted Bacterial Infection (TTBI) PI and BS before and after implementation for two large blood providers.
Optimal Time to Treat/Sample
One fundamental difference is the optimal timing of each intervention. PI must be performed as early as possible to prevent bacteria from multiplying to high concentrations, which may overwhelm the inactivation capability of the system. BS operates according to the opposite principle. Sampling needs to occur as late as operationally feasible, allowing initially low concentrations of bacteria sufficient time to grow to detectable levels. This distinction has important logistical implications and may strongly influence which approach is most suitable for a particular blood service.
Range of Microbial Activity
An important advantage of PI is its broad antimicrobial activity and may provide protection against certain emerging pathogens. However, it does not inactivate all pathogens. Whereas, BS only detects bacteria and fungi.
Identification of organisms in Platelet Components (PC) supply and surrogate screening of associated components
BS determines the presence of contaminant organisms in the PC inventory, providing data that can be used to monitor the effectiveness of the sampling technique, donor arm disinfection and aliquot diversion. PC BS results could also indirectly detect disease in donors. Furthermore, a positive PC result can trigger investigation of associated components. In contrast, PI does not have these advantages.
System Achilles Heels: Bacterial Spores/Bacterial Toxins/ Staphylococcus aureus
Current PI systems do not inactivate bacterial spores or bacterial toxins. This represents one of the recognised biological vulnerabilities of PI. Staphylococcus aureus remains an important challenge to BS. Repeated failures to detect this organism using BS have been cited in the literature. The reasons for this failure of detection maybe multifactorial.
Shelf extension
Both approaches can support extended platelet shelf life, including seven-day storage strategies, which has been shown to reduce expiry rates. Neither system gives a full 7 days of shelf life.
Removal of Irradiation and CMV Screening
PI will allow the removal of Gamma Irradiation and Cytomegalovirus (CMV) screening, due its killing of leucocytes. BS does not change the need for irradiation and CMV screening.
Loss of Product Volume/Platelet Function/Increased Donor Exposure
Both systems result in a loss of PC volume. In addition, PI results in a loss of platelet function and may require a greater frequency of transfusion. To meet the strict guardbands for PI, increased pool sizes have been needed by some blood services increasing patient donor exposure.
Loss of Product/Recalls and Cost
BS is associated with product loss and recall. The extent of this is dependent on the initial reactive rate. PI is associated with minimal product loss and recall. The basic cost for PI is higher than BS, but this needs to be addressed holistically on the organisation requirements. Cost-effectiveness considerations are complex.
Evidence for the Efficacy of PI and BS
National data from Établissement français du sang (EFS), France and NHSBT, England provide compelling evidence of the effectiveness of both interventions. Table 1 presents data before and after implementation. The risk of transmission is reduced to near or more than one million. The data sets are not directly comparable the French denominator represented transfused components, and the NHSBT tested components. Also, the surveillance systems are not the same. Nevertheless, both datasets demonstrate extremely low residual risks. The breakthrough organisms highlight different vulnerabilities as previously mentioned (Table 2). In France, four of six breakthrough-related events involved Bacillus species, a spore former. In the NHSBT dataset, seven of nine breakthrough events involved S. aureus.
Table 2. Species Implicated in TTBI and Near-Misses at EFS, France, and NHSBT, England
Conclusion
In the situation where blood services have not implemented either strategy to reduce bacterial contamination of PC, the absence of recognised bacterial reactions must not be interpreted as evidence that no risk exists. The option of doing nothing is increasingly difficult to justify when two highly effective risk-reduction strategies are available. PI and BS both substantially improve platelet safety. They have different strengths, weaknesses and operational requirements, and neither eliminate all risk. Blood services need to select and effectively implement the system that best fits their organisational requirements.
References
1. Laperche S, de laTaille V, Gallian P, Pouchol E, Humbrecht C, Montembault A, et al. Pathogen-reduced platelet concentrates in France: Impact on the risk of transfusion-transmitted infections, 2017–2024. Vox Sang. 2026;121:581–586. 2. NHSBT/UKHSA Epidemiology Unit: Quarterly Bacterial Screening of Platelets Report: October – December 2024 3. Narayan, S. et al., 2025. The 2024 Annual SHOT Report, Manchester: Serious Hazards of Transfusion (SHOT) Steering Group.
