Risks associated with red blood cell transfusions: potential benefits from application of pathogen inactivation

Kleinman, Steve; Stassinopoulos, Adonis

A comprehensive CDC review reported 162 transfusion-transmitted babesiosis (TTB) cases (28 fatalities) in the United States between 1979 and 2009. 20 Since cases were compiled by passive surveillance, this is very likely an underestimate. B. microti was the agent in 159 cases while three involved B. duncani. All but four cases were from RBC units with transmission occurring throughout the storage period. Almost 80% were reported from 1999 to 2009; whether this represents increased transfusion transmission or lack of recognition of past cases or both is not known. Although nearly 90% of cases were in the seven highly endemic states, cases also occurred in nonendemic states. 20, 22 These were attributed to shipment of RBC units from an endemic to a nonendemic area, a donor from an endemic area donating while visiting a nonendemic area, or a nonendemic area donor having acquired the infection while visiting an endemic area. In the absence of additional interventions, known per-unit infectious risks are consistent over time. These risks change when an EIA enters the blood supply. The figure indicates two types of EIAs: an acute agent and a chronic agent.* A past example of an acute EIA is West Nile virus and a past example of a chronic EIA is HIV. In contrast to known agents, EIA risks will vary over time. The intervals between an acute or chronic EIA entering the blood supply and the application of a successful intervention for that agent have been estimated as 1.5 and 5 years, respectively. After recognition of the EIA and development of a screening test, the risk from that agent will be decreased but a small residual risk will remain, thereby slightly increasing the overall per-unit risk above the previous level. This is indicated (though not to scale) by the stepwise increase in the horizontal line. *An acute agent is present only transiently (usually days to weeks) until the donor resolves the viremia or parasitemia. In contrast, the donor retains the chronic agent in their blood for many years (perhaps an entire lifetime) while remaining asymptomatic and capable of blood donation.