Beat M. Frey, E. Skalsky, M. Frey-Wettstein Stiftung Zürcher Blutspendedienst SRK, 8001 Zürich

Since more than a decade, it is well established that rigorous pre-storage leukodepletion of whole blood donations substancially improves preservation, storage and tolerance of blood component products (BCP) as well as reduces risks of transfusion associated (ta) infectious diseases, ta-HLA senisitization and ta-immunmodulation. However, only the most recently revived debate on prevention of ta-prion diseases, such as vCJD, prompted the costly introduction of universal leukodepletion (ULD) by law. In Switzerland, since 1.7.1999 ULD is mandatory for all transfused BCP. In general, ULD is provided by filtration, except some BCP produced by apheresis are leukodepleted by alternative techniques.

Vigorous evaluation, validation as well as adequate and sustained process control of ULD are required to meet the goal of intended quality improvement of BCP by ULD. Therefore, we retrospectively scrutinised filtration data of red cell concentrates (RBC) provided by 7 Swiss blood transfusion services (BTS) applying the same leukofiltration procedure of whole blood. The main objectives of our analysis were filtration efficacy, filtration capacity, data modulating covariables and biocompatibility of filtration procedure applied. To complete our study, we inquired key validation data of filtration procedures applied by the remaining 6 Swiss BTS using a standardized questionnaire. Therefore, our study gives a comprehensive overview of the quality of ULD of RBCs in Switzerland.

Results and Conclusions:

  • 97% - 100% of leukodepleted RBCs fulfill the product specification of residual white blood cells (rWBC) as issued by the Swiss Red Cross, being < 106 rWBC/unit (European standard). 100% of leukoreduced RBCs fulfill the US standard (rWBC < 5x106/unit).
  • The majority of RBCs contain < 105 rWBC/unit
  • Filtration temperature is the main determinant of filtration efficacy
  • The currently used blood filters provide sufficient filtration capacity for adequate filtration of whole blood, donated by healthy and properly selected donors
  • For technical and statistical reasons, quality assurance of ULD should be performed by modern laboratory technology such as flowcytometry.
  • Red cell loss by filtration may reach 20% and is mainly due to dead space of the filtration device. There is no indication of inappropriate hemolysis due to the applied filtration material.