Editorials

Safe tissue grafts

Orthopaedic patients receiving transfusions may worry about the safety of the blood they receive but be blissfully unaware of the possible risks associated with the allograft bone in their femur or hip. Any fears about blood transfusion are largely unfounded. Blood donors in Britain are unremunerated volunteers who are carefully selected and screened by the National Blood Transfusion Service, and donated blood is processed and tracked in a highly regulated environment in which biannual inspections result in the issue of special licenses by the Medicine Control Agency.

Tissue banking in Britain is under no such quality control. In total hip replacements the femoral head, which would otherwise be discarded, may be banked for transplantation to other patients, most commonly in revision hip surgery.¹ Cadavers provide an alternative source of donor bone. A tissue bank can be established by any organisation without regard to licensing, inspection, or adherence to any standards. There is evidence that many bone banks in hospitals operate suboptimal standards.²

Transmission of viral, bacterial, and fungal pathogens has been reported from most types of tissue commonly transplanted.³ Testing reduces the risks of transmission, but safety also relies on careful selection of donors on the basis of their medical and social history. The volunteer status of a cadaver tissue donor is clearly not comparable to that of a blood donor. Surgical patients who become tissue donors are actively approached pre-operatively to consider donation, as are the families of potential cadaveric donors. Additional risk arises from the inability to take first hand medical and social histories from those who donate tissues after death. Information must be gleaned from relatives, general practitioners, and pathologists, with particular emphasis on potential transmission of diseases of unknown aetiology, such as sarcoidosis, Parkinson's disease, and malignancy.

Unlike blood, many non-viable tissues can be cleared of bacteria, and possibly viruses, by exposure to ionising radiation or ethylene oxide gas. Even minimal processing of tissues seems to reduce the risk of HIV transmission.⁴ However, when tissue viability is required this is not an option.

These risks must be seen in the context of considerable unmet demand, particularly for allograft bone, which could create pressures to lower the standards of donor selection. Recognising the rapid growth of tissue banking in Britain and the associated risks, the Department of Health conducted a national review.

Living tissue donors have been required to undergo repeat testing for HIV antibodies, and other markers tested mandatorily in blood donors, 180 days or more after donation, and guidance has been given on the selection and testing of tissue donors, bacteriological safety of donations, storage and transportation of organs and tissues, and the effect of haemodilution of the donor on the validity of tests.⁵

The British Association of Tissue Banks has published standards for the selection, testing, and processing of tissues,⁶ and the association is also developing technical manuals. Many tissue banking activities are undertaken within the National Blood Service in recognition of the similarities between blood and tissue banking.^{7 8} Guidelines for the Blood Transfusion Service⁹ will shortly include a section on tissue banking, encompassing donor selection, tissue processing, and tracking of tissues from donor to recipient. The tissue banking community is working towards common standards to ensure the safety of tissues for transplantation.

However, common standards alone do not equate with the highly regulated environment in which blood is collected and processed. In the United States, despite the existence of detailed tissue banking standards¹⁰ and a system of voluntary accreditation, the Food and Drug Administration considered it necessary to introduce legislation governing tissue banking activities.¹¹

So where do we stand in Britain? No legislation exists to allow the inspection and regulation of tissue banks. Options include a system of voluntary registration, with peer review against agreed standards, and the inclusion of tissues, with blood, in the brief of the Medicines Control Agency inspectorate. In our view voluntary registration with peer review would be an effective preliminary step towards ensuring the safety of transplanted tissues. This would allow all tissue banks to institute appropriate procedures and documentation. Agreed standards should evolve with time, gradually increasing in their stringency, and should be based on the existing work of the British Association of Tissue Banks and the National Blood Service guidelines. Whether standards comparable to those in the Blood Transfusion Service can be achieved without recourse to legislation and regulation remains to be seen. Whichever option is chosen, it is essential that every patient benefiting from a tissue donation can be confidently reassured that agreed safety standards have been complied with in the provision of the graft.

D Fehily, Head of tissue services,^a R M Warwick, Lead consultant for tissue and stem cell donor care ^a

^a National Blood Service, London and the South East, North London Blood Centre, London NW9 5BG

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5. Committee on Microbiological Safety of Blood and Tissues for Transplantation, Department of Health. Guidance on the microbiological safety of human tissues and organs used in transplantation. London: NHS Executive, 1996.
6. British Association of Tissue Banks. Standards for tissue banking, June 1995. Transplant Med 1996;6:155-8.
7. Warwick RM, Eastlund T, Fehily D. Role of the blood transfusion service in tissue banking. Vox Sang 1996;71:71-7.
8. Myers SR, Machesney MR, Warwick RM, Cussons PD. Skin storage. National blood transfusion centres could take on skin banking and distribution. BMJ 1996;313:439. [Free Full Text]
9. Guidelines for blood transfusion service. 2nd ed. London: HMSO, 1994.
10. American Association of Tissue Banks. Standards for tissue banking. Bethesda, MD: American Association of Tissue Banks, 1996.
11. United States Food and Drug Administration: Interim rule: human tissue intended for transplantation. Federal Register. 21 CFR Sect 1270.58:65514-21 (1993).