Studies on the improvement of leucodepletion performance of the Haemonetics MCS+ for production of leucodepleted platelet concentrate.

With the implementation of universal leucodepletion, an in-line, negatively charged LRF6H leucodepleting filter became an essential part of the Haemonetics MCS+ plateletpheresis system. A larger-scale (968) study using the standard protocol revealed a 2.79% leucodepletion failure rate (standard < 5 x 10(6) leucocytes per adult therapeutic dose). Factors influencing the efficacy of the filter were investigated. The pH of the filtrate was 7.0, the temperature 28 degrees C and filtration rate 80 ml/min. Reduction of the filtration rate to 30 ml/min (784 doses) reduced leucodepletion failure to 0.38%. Measurement of the leucocyte count, pre- and post-filtration of the platelet products, revealed that donations from 1% of donors contained substantially larger numbers of leucocytes in pre-filter samples (300-1500/microl) than in control samples (35-70/microl). This number tends to increase progressively with subsequent donations in these individuals, leading to leucodepletion failure, whilst peripheral leucocyte counts remain normal. The new continuous filtration protocol (version C) using a less impact filter LRF-XL and a lower (7 ml/min) head pressure was also effective but failure still occurred twice on one of the donors who persistently showed high pre-filter count. We conclude that leucodepletion failures in the Haemonetics system are related to both donor leucocyte (i.e., being light and non-adherent) and operational/filter performance.