ASSESSMENT OF FILTRATION PROCEDURES

The technique of filtration which has constantly been improved over pa st years makes it possible to obtain highly pure blood products (the r ate of leukocyte depletion can reach 3 to 5 log). Several study groups (BEST, PSL) and international commitees of experts have defined a num ber of standards with which leukocyte depleted blood products must com ply. Assessment of filration procedures is thus made necessary, it app lies to the different steps of the filtration procedure: preparation t echniques of red cell or platelet suspension, priming and rinsing of t he filter. Likewise a number of parameters have to be checked: filtrat ion time, temperature, age of suspensions. Moreover quality control pr ocedures must be implemented, using adapted and validated measuring me thods (Nageotte hemacytometer, for instance). The parameters to be mon itored include the number of residual leukocytes, (mean value : 1 x 10 (6) i.e. about 4 WBCs/mul), and the rate of hemoglobin or platelet rec overy. Any new filtering equipment or material must satisfy strict req uirements and standards including clinically acceptable limits as part of the same quality approach. Validation, in this case, consists in d etermining the maximal leukocyte content which the filter can absorb ( capacity) and the average rate of leukocyte removal (efficacy). The co nstant monitoring of filtration performance contributes to improving t he quality of red blood cell or platelet suspensions a nd thus meet cl inicians' requirements for their patients.