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Joint Statement Before Secretary’s Advisory Committee on Xenotransplantation – 3/12/02


March 12, 2002

Presented by Kay R. Gregory, MS, MT(ASCP)SBB
Director, Regulatory Affairs, AABB

Recognizing the potential risk of transmitting zoonotic pathogens to patients by xenotransplantation, the American Association of Blood Banks (AABB), America’s Blood Centers (ABC), and the American Red Cross (ARC) agree that xenotransplant recipients are unacceptable donors of allogeneic blood and tissue. Under current donor restrictions regarding health and medication use, virtually no xenotransplant recipient would be a qualified blood donor at this time.

The theoretical risk from zoonoses was well articulated in August 1996 in the Draft Public Health Service (PHS) Guideline on Infectious Disease Issues in Xenotransplantation, which included language appropriately recognizing the primary responsibility of the transplant community for the apprisal of their patients about zoonotic risks. At its January 13, 2000 meeting, the Xenotransplant Subcommittee of the Biological Response Modifiers Advisory Committee endorsed our position that primary responsibility for notification and education of xenotransplant recipients about refraining from blood and tissue donation lies with the institution performing the clinical trial.

The AABB, ABC, and ARC strongly support implementation of this aspect of the Food and Drug Administration’s (FDA) most recent draft guidance. Blood collection facilities can reinforce the prohibition on donation by including the xenotransplant exclusion in the written materials blood donors are required to study before each donation. This avoids addition of time-consuming, confusing, and unvalidated questions that FDA suggests adding to the donor interview in this guidance.

Donor screening is already lengthy and complex. The AABB Uniform Donor History Questionnaire (sanctioned by FDA) contains 32 separate elements, including inquiries into highly sensitive personal areas of sexual activity and drug use and references to such rare diseases as Babesiosis and the transmissible spongiform encephalopathies.* FDA proposes to add additional complex questions to this process. REDS investigators have reported that 1.8% of anonymously surveyed accepted blood donors admit to deferrable risks, and we suspect that a substantial proportion of that percentage is due to the length and complexity of the donor interview.

An AABB-sponsored interorganizational task force on streamlining the donor history questionnaire has recently conducted focus group evaluation of the xenotransplantation questions proposed by FDA in their current iteration. They provoked multiple recommendations for editing and shortening the questions, splitting questions into their component parts, and more precise definition of such terms as "repeatedly" and "deep kissing."

Increasing the complexity of the donor screening process for marginal theoretical risks will detract from its efficacy for documented risks like traditional viral transfusion associated infections and malaria. The result may be a paradoxical decrement in transfusion safety, in addition to any unintended donor loss.

The AABB, ABC, and ARC maintain that proposed donor questions in this draft guidance remain too arcane to add to the current screening process and may produce donor confusion. This would result in unneeded deferrals at a time of borderline blood supply adequacy. At a minimum, additional questions proposed by FDA for the reduction of hypothetical risk must be validated for comprehension before being added to what is already referred to as the "donor interrogation" process.

The requirement for deferral of sexual, household, and other close contacts is unsupported by any evidence of transmission of potential or unrecognized pathogens to such non-immunosuppressed contacts after exposure to xenotransplant recipients. The AABB, ABC, and ARC understand that the xenotransplantation recipient will be immunosuppressed and be at theoretically increased risk from zoonoses. We do not accept that the non-immunosuppressed contacts are at increased risk and object to their inclusion. In the prior draft, deferral of "health care workers, laboratory personnel, and other individuals who have had contact with blood and body fluids from a xenotransplantation product recipient…" was subject to the same criticism, and this language has been dropped from this most recent draft. Furthermore, it is a slippery slope from such donor deferrals to disqualification of larger populations with significant occupational animal exposures, such as abattoir workers, farmers, veterinarians, and medical researchers.

The AABB, ABC, and ARC suggest that a risk assessment be undertaken among non-xenotransplant individuals with close contact to the relevant animal species for evidence of disease associations that would support concerns of zoonotic transmission of disease causing organisms by donor blood. Given the small numbers of xenotransplants currently being performed and the potentially large populations with contact to nonhuman primates and swine, these epidemiological studies can be carried out before xenotransplantation becomes prevalent, constituting a zoonotic threat to significant numbers of patients and their contacts.

In summary, the AABB, ABC, and ARC would like to stress the following points:

  • We accept the necessity to defer recipients of xenotransplants, and respectfully suggest that the transplant programs have primary responsibility to initiate this process as part of informed consent.
  • Blood collection facilities can reinforce this action with written predonation information.
  • The addition of unvalidated donor interrogation questions for the theoretical risks of xenotransplantation (or any theoretically transmissible entity) may, at worst, paradoxically increase other risks of transfusion, and at best will contract further an already shrinking donor base. At a minimum, such proposed questions must be validated for a minimum level of sensitivity, specificity and predictive value, as would any in vitro diagnostic assay required by FDA.
  • Deferral for contact with xenotransplant recipients is unwarranted at present and the risk of such contact is amenable to study in populations with occupational exposure to the relevant species.

*Note: The American Red Cross uses a similar, but not identical, blood donor history questionnaire.