ASSESSMENT OF FILTRATION PROCEDURES

The technique of filtration which has constantly been improved over past years makes it possible to obtain highly pure blood products (the rate of leukocyte depletion can reach 3 to 5 log). Several study groups (BEST, PSL) and international commitees of experts have defined a number of standards with which leukocyte depleted blood products must comply. Assessment of filration procedures is thus made necessary, it applies to the different steps of the filtration procedure: preparation techniques of red cell or platelet suspension, priming and rinsing of the filter. Likewise a number of parameters have to be checked: filtration time, temperature, age of suspensions. Moreover quality control procedures must be implemented, using adapted and validated measuring methods (Nageotte hemacytometer, for instance). The parameters to be monitored 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 recovery. Any new filtering equipment or material must satisfy strict requirements and standards including clinically acceptable limits as part of the same quality approach. Validation, in this case, consists in determining the maximal leukocyte content which the filter can absorb (capacity) and the average rate of leukocyte removal (efficacy). The constant monitoring of filtration performance contributes to improving the quality of red blood cell or platelet suspensions a nd thus meet clinicians' requirements for their patients.