New safety assurance for biological skin covers

The described system of safety assurance of cryopreserved allogeneic and xenogeneic dermoepidermal transplants comprises serological examination of deceased tissue donors, long-term storage of sera of all donors, microbiological control of prepared allogeneic and xenogeneic dermoepidermal grafts, labelling of released tissue grafts and monitoring of temperatures inside the mechanical freezer (-80 degrees C). From a total number of 76 donors from whom tissues were collected for transplantation during 1999-2001, tissues were discarded in two instances. One because of a positive HBsAg test, the others second one because of presence of anti-HTLV antibodies. In xenogeneic dermoepidermal grafts, out of a total number of 1,203 grafts prepared during the same period, 84 (6.9%) were discarded because of the presence of pathogeneic or potentially pathogeneic microbes. The system of labelling released grafts makes unequivocal identification of the pathway from recipient to donor possible, while at the same time respecting the anonymous character of the donor's data. In xenogeneic grafts it ensures the identification of the appropriate batch. Storage of cryopreserved biological skin covers at a temperature of -80 degrees C in low temperature cabinets with emergency back-up cooling with liquid nitrogen and a supplementary source of electric power, proved very useful. The system responds to the gradual implementation of the principles of Quality Management System ISO 9000 and Good Manufacturing Practice into the activities of tissue banks. Further tightening of the demands for the safety of allo- and xeno-transplantation is foreseen in conjunction with the occurrence of transmissible spongiform encephalopathy and porcine retroviruses.