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.

Leukoreduction of Platelet Concentrates Using a &lsquo;Polishing&rsquo; Filter

“…These results are supported by accumulated routine quality control (QC) data from our blood centre that suggest that with the use of PAS–II, the platelet yields are considerably lower compared to the PCs prepared in plasma. In our current routine production method, PCs are leukoreduced with the Autostop™BC filter (produced by Pall Medsep), but in contrast to the earlier published results [9], PAS–II is now used. PCs in plasma and filtered with the Autostop filter contained a median number of 340×10 9 platelets per unit (n = 15,037 from January 1996 until September 1997) [9], while in PAS–II, the PCs contained a median number of 310×10 9 platelets (n = 3,179 from August 1998 until June 1999) (current QC data).…”

“…These PRP units have on average a high leukocyte content of 0.2–1×10 6 /ml before filtration [1, 8], so for the filter a high leukocyte–reducing capacity is mandatory. The second method is generally applied for filtration of PCs from pooled BCs [3, 9], although it can also be used for PRP filtration [8]. This method allows prestorage leukoreduction.…”

“…This method allows prestorage leukoreduction. The filter is placed in line between the BC pooling bag and the final storage bag [9], integrated in the system or by the use of a sterile connection device. The platelet–rich supernatant (PRS) is expressed to the storage container through the filter, and therewith leukoreduced [9].…”

“…The filter is placed in line between the BC pooling bag and the final storage bag [9], integrated in the system or by the use of a sterile connection device. The platelet–rich supernatant (PRS) is expressed to the storage container through the filter, and therewith leukoreduced [9]. With the latter system, especially with a large housing of the filter, the high numbers of platelets concentrated just above the interface of red cells and plasma are lost.…”

Quality of Transfusion Products in Blood Banking

“…Prestorage leukocyte depletion is recommended (within 6 hours after preparation if performed by filtration). [23][24][25] The three products may be stored in an additive solution to minimize the risk of transfusion reactions associated with plasma proteins and prevent the risk of transfusion-related acute lung injury. 26 Cryopreserved platelets are prepared by the freezing of platelet concentrates at À80°C within 24 hours of collection using a cryoprotectant (dimethyl sulfoxide 6% weight/ volume or glycerol 5% weight/volume).…”