Transfusion-Transmitted Diseases

Published on 04/03/2015 by admin

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Chapter 54 Transfusion-Transmitted Diseases

Louis M. Katz, Jay E. Menitove

Blood Safety Decision Making

Most consider the blood supply in the developed world to be at its highest historical safety level. This reflects incremental improvements in donor selection and history screening, blood testing, and process control that span four decades. For years, blood collection professionals and government regulators formulated blood safety policy decisions on the premise that a zero-risk blood supply was achievable. In part, this reflects the perceived tardy transfusion medicine community’s response in the early 1980s to the emergence of human immunodeficiency virus (HIV) in the blood supply and the recognition (of) the scope and severity of posttransfusion non-A, non-B hepatitis (subsequently hepatitis C [HCV]) following that. It reflects also the “dread fear” associated with transfusion-associated HIV. This visceral reaction occurs when devastating, unpredictable, and stigmatizing events threaten potential victims who have minimal avoidance discretion. This fear was validated by numerous transfusion-related HIV cases. It was amplified by widely publicized lawsuits, indictments, and criminal convictions of health ministers and policy makers in the 1980s and 1990s (l’ affaire du sang contaminé in France addressing HIV and Canada’s Royal Commission of Inquiry on the Blood System into blood collection agencies’ response to non-A, non-B hepatitis risk).

Not surprisingly, from the 1980s until now, donor deferrals and blood-testing interventions have been rapidly, successively, and additively implemented for emerging and theoretical risks. Collection facilities introduced anti-HBc and alanine aminotransferase (ALT) testing as surrogates for non-A, non-B hepatitis, HIV p24 antigen testing, then nucleic acid testing (NAT) for hepatitis C, HIV, extensive deferrals for the risks attending transmissible spongiform encephalopathies (TSEs,) NAT for West Nile virus (WNV) and hepatitis B, and antibody testing for Trypanosoma cruzi. The cost-benefit estimates for some of these interventions exceeded by orders of magnitude generally accepted thresholds but did not deter their adoption. For example, the costs per quality-adjusted life-year proximate to implementation include HIV NAT, $1,966,000; HCV NAT, $1,830,000; WNV NAT, $520,000 to $897,000; human T-lymphotropic virus (HTLV) antibody testing, $63,000,000; and T. cruzi antibody testing, $2,123,000 (Fig. 54-1). It is unlikely that this reactive approach can be sustained in the current health care–reform environment.

Application, after HIV entered the blood supply, of a stringent form of the precautionary principle (originally promulgated for environmental protection, not transfusion safety) pushed decision making toward avoidance of all risks. The precautionary principle promotes implementation of measures to mitigate risk even if evidence of a risk is incomplete. It is supposed to be tempered by proportionality; that is, any measures adopted are to be proportional to the risk and with those used in similar circumstances, but some have argued that this has not been the case with blood safety measures, at least by the metric of cost-benefit. Nevertheless, although in potential conflict with evidence-based decision making, this approach resonated with policy advocates charged with transfusion safety. The impact on transfusion safety is mixed. In retrospect, the implementation of HIV p24 antigen testing in the mid-1990s despite enormous studies demonstrating its lack of utility was extreme. Likewise, the recent decision to defer donors with chronic fatigue syndrome, based on a single study, to prevent xenotropic murine leukemia virus–related virus (XMRV) transmission was not necessary. Continued lifetime deferral of men having sex with men even once since 1977 is seen by many to be discriminatory in light of increasingly sensitive in vitro tests and alternative approaches to other risk behaviors. In contrast, when the risk for transfusion transmission of vCJD was theoretical, modeling was used to balance any such danger against the impact of broad donor deferrals on the adequacy of the blood supply and to arrive at a policy decision. Some argue that the magnitude of risk does not justify the stringency of donor criteria and number of resulting deferrals given the tiny risk in a country that is not bovine spongiform encephalopathy (BSE) endemic, but the process was rational and should perhaps be seen as a precedent that “an acceptable risk” is estimable.

Hemovigilance programs, such as the Serious Hazards of Transfusion (SHOT) in the United Kingdom and others in Canada, France, and a fledgling program in the United States, have emerged, supplying evidence about a much broader range of transfusion hazards than just infections. For example, a data-driven decision to minimize plasma transfusions from potentially alloimmunized female donors resulted in a dramatic reduction in transfusion-related acute lung injury in the United Kingdom, and early studies in the United States are consistent with this effect.

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