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

Kleinman, Steve; Stassinopoulos, Adonis

There are no FDA-licensed blood donor screening assays. Recently, B. microti donor screening using serologic (automated immunofluorescence or enzyme-linked immunosorbent assay) and nucleic acid test (NAT) assays under an investigational new drug procedure has been ongoing on a portion of the inventory in several states. [24] [25] [26] [27] Seroprevalence in these states ranged between 0.4 and 1.2% (17% being polymerase chain reaction [PCR] positive) and 1 in 10,000 donors showed PCR positivity without antibody. 27 Although PCR positivity increases the risk of transfusion transmission, PCR-negative but seropositive units may also transmit; furthermore low-level parasitemia or infectivity may be intermittent over a period of months to a year. [27] [28] [29] Whereas there have been no TTB cases from Babesia-negative RBC units, the TTB rate in these regions from unscreened units has ranged from 1 in 20,000 to 1 in 31,000 over the same time interval. 22 These data suggest that a dual serology and NAT approach is needed to maximize risk reduction. 26, 27 Given that B. microti is a mostly intracellular organism, this would require PCR testing of cellular material, which is logistically more challenging than the plasma NAT performed for other pathogens. Further, since Babesia infection is regional, a blood center's impetus to screen donations upon FDA licensure is likely to vary. In nonendemic areas, reluctance may be due to concerns about adding unnecessary cost for little safety gain and the loss of donors due to false-positive test results. 30 Finally, there is no legal or ethical precedent or model for regional screening of the US blood supply. These issues could be made moot by the use of PI-RBCs.