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Statement Before the Xenotransplantation Subcommittee of the Biological Response Modifiers Advisory Committee – 1/13/00

Statement of the American Association of Blood Banks before the Xenotransplantation Subcommittee of the Biological Response Modifiers Advisory Committee

January 13, 2000
Presented by Kay R. Gregory, MS, MT(ASCP)SBB
Director Regulatory Affairs

The American Association of Blood Banks (AABB) is the professional society for over 9,000 individuals involved in blood banking and transfusion medicine and represents roughly 2,200 institutional members, including community and Red Cross blood collection centers, hospital based blood banks, and transfusion services as they collect, process, distribute, and transfuse blood and blood components and hematopoietic stem cells. Our members are responsible for virtually all of the blood collected and more than 80 percent of the blood transfused in this country. For over 50 years, the AABB’s highest priority has been to maintain and enhance both the safety and availability of the nation’s blood supply. The Association operates a wide array of programs to meet this safety and availability priority and is proud to have played a key role in ensuring that the nation’s blood supply is safer today than ever before.

The AABB appreciates this opportunity to comment on the draft guidance document addressing the potential deferral of donors due to precautionary measures to reduce the possible risk of transmission of Zoonose by blood and blood products from xenotransplantation product recipients and their contacts.

Xenotransplantation is an exciting emerging technology that holds future promise for ameliorating the shortage of donor tissues for the treatment of serious, disabling diseases. Recognizing the important potential risk of transmitting zoonotic pathogens to patients by this route, we agree that xenotransplant recipients are unacceptable donors of allogeneic blood and tissue. Parenthetically, because of donor restrictions regarding medication use and general health, virtually no xenotransplant recipient would be a qualified blood donor at this time. The theoretical risk was well articulated in August 1996 in the Draft Public Health Service (PHS) Guideline on Infectious Disease Issues in Xenotransplantation which states "Consent forms should state clearly that xenograft recipients should never, subsequent to receiving the transplant, donate Whole Blood, blood components, Source Plasma, Source Leukocytes, tissues, breast milk, ova, sperm, or any other body parts for in humans." The language appropriately recognizes the primary responsibility of the transplant community for the apprisal of their patients about zoonotic risks.

We believe strongly that this aspect of the HHS guidance should be implemented. Even pending formal implementation of such guidance, FDA can insist on inclusion of such information in consent procedures as a condition for acceptance of clinical protocols for xenotransplantation. The FDA can also require that all current surviving xenotransplant recipients be contacted to assure that they understand they must not donate blood or tissue. 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 to the donor interview.

That said, several aspects of the draft guidance are problematic. Donor screening is already lengthy and complex. We have provided committee members with a copy of the most recents AABB Uniform Donor History (sanctioned by FDA) which 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 three complex questions to this process. REDS investigators (Williams et al. JAMA. 1997) have reported that 1.8% of anonymously surveyed accepted blood donors admit to deferrable risks, and we suspect that a substantial proportion of that is due to the length and complexity of the donor interview. The proposed donor questions in this draft are far too arcane to add to the current screening process and will produce donor confusion. In fact, the individuals that I asked to review these questions unanimously agreed that there were not understandable. This will result in unneeded deferrals at a time of borderline blood supply adequacy and declining donations. At a minimum, additional questions proposed by FDA for the reduction of de minimis risk must be validated for sensitivity, specificity and positive predictive value before being added to what is already referred to as the "donor interrogation" process. Further antagonism of the altruistic blood donor is unwarranted by current data.

A related concern is that increasing the complexity of the donor screening process for marginal theoretical risks may detract from its efficacy for documented risks like traditional viral transfusion associated infections and malaria. The result is then a paradoxical decrease in transfusion safety.

The requirement to defer as blood donors "sexual partner(s), any member of your household, or any other close contact" is ambiguous (lacking concise definition of household and other close contact). More important, this requirement for deferral is unsupported by any evidence of transmission of potential or unrecognized pathogens to such contacts after xenotransplantation. It is a slippery slope from such donor deferrals to disqualification of large populations with significant occupational animal exposures such as abattoir workers, farmers, veterinarians, and medical researchers working with large animal models. We suggest that a risk assessment be undertaken among those with close contact to the relevant species for evidence of transfusable disease associations that would support zoonotic transmission of disease causing organisms. 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 long before xenotransplantation becomes prevalent.

In summary:

  • We accept the necessity to defer recipients of xenotransplants but respectfully suggest that the transplant programs have primary responsibility to initiate this process as part of the consent process. Blood collection facilities can reinforce this with written information.
  • We suggest that the addition of unvalidated donor interrogation questions for the theoretical risks of xenotransplantation may, at worst, paradoxically increase other risks of transfusion, and at best will contract further an already shrinking donor base.
  • 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