Preparation of Leukodepleted Platelet Concentrates from Pooled Buffy Coats: Prestorage Filtration with Autostop™BC

Abstract

Background and Objectives: Our requirements for leukocyte–depleted platelet concentrates (LD–PC) for an adult patient are: platelets >240×10⁹, leukocytes <5×10⁶, volume of 150–400 ml; and at the end of storage a pH between 6.8 and 7.4 and presence of the swirling effect. Our aim was to develop a standardized, semiautomated method for the production of LD–PC, by pooling of buffy coats (BC), and prestorage leukoreduction by filtration. Materials and Methods: Whole blood was collected in Top and Bottom systems, and separated automatically with the Compomat^™ G3 equipment into a red cell concentrate, a plasma and a BC. Subsequently, a pool of 5 BC was made, and 200 g plasma from one of the donors was added. Then, after soft spin centrifugation, the platelet rich plasma was leukocyte depleted by filtration using the Autostop^™BC filter, and stored in a 1,000 ml polyolefin platelet storage bag. Results: BC (n = 60) had a volume of 51±2 ml (mean ± SD) with a hematocrit of 0.44±0.03 l/l and contained 80±5% of the platelets and 74±12% of the leukocytes of the whole blood. Routinely prepared LD–PC (n = 15,037) contained a median of 341×10⁹ platelets (range 49–599×10⁹), with only 104/15,037 (0.7%) containing fewer than 240×10⁹ platelets; the median volume was 263 ml (range 134–373 ml). In 118/917 (13%) LD–PC leukocytes were observed in the Nageotte hemocytometer, but only twice exceeding 1×10⁶ leukocytes per unit, and none exceeding 5×10⁶ (median <0.6×10⁶; range <0.6–1.41×10⁶). Storage experiments of the LD–PC (n = 12) revealed adequate oxygenation and maintenance of pH and swirling effect up to 9 days. Conclusions: This method warrants with 99% confidence that LD–PC contain more than 240×10⁹ platelets; with 97.5% confidence that 100% of the LD–PC contain <5×10⁶ leukocytes, and with 95% confidence that more than 99% of the LD–PC contain fewer than 1×10⁶ leukocytes; these LD–PC can be stored satisfactorily for up to 9 days.