Validation of different enrichment strategies for analysis of leucocyte sub-populations: development and application of a new approach, based on leucofiltration.

Characterisation of the nature of leucodepletion failure, based on the analysis of leucocyte sub-populations, is an essential task for continual improvement in the clinical safety of blood components and for the selection of a safe and appropriate leucodepletion process. Such information is also critical for improving the quality of filters through an understanding of the mechanism of leucocyte removal filters. Unfortunately, the residual leucocytes of filtered blood components are around the sensitivity of current leucocyte-counting technologies, hence a need for an enrichment process. This preliminary report deals with the merits of various WBC enrichment strategies for the analysis of WBC sub-population subsets. A new procedure, based on refiltering and backflushing the content, with up to 30-fold enrichment, is described. This one-step procedure has the advantage of concentrating both native and atypical leucocytes seen in blood components. The latter may account for lack of interchangeability of results obtained by various counting methods.