Evaluation of elutriated single donor platelets collected and stored in a closed system.

Single donor platelets (SDPC) were collected by the elutriation technique in a closed-system integrated with large storage containers. Seven runs of SDPC were stored in a 1.5 liter polyvinyl-chloride trimellitate (PVC-TOTM) storage container, making the ratio of platelet concentrate volume to container volume 1:4.5. An equal volume of pooled multiple donor platelet concentrates (MDPC) was stored in parallel under the same conditions. All haematological data were comparable for both products, except for the degree of leukocyte contamination (5-fold increase in the pool). Under these conditions, the functional, morphological, and metabolic characteristics of elutriated platelets throughout 7-day storage were superior to those of pooled platelets. Although the platelet count was not significantly different in both types of concentrates, the mean pH of pooled MDPC fell to 6.0 on day 5 of storage. Leukocytes were shown to contribute to this pH fall. The extent of cell damage, however, as evidenced by LDH leakage (42.7 LDH units/10(11) platelets/day by differential centrifugation, compared to 5.3 units by elutriation) could not be explained solely on the basis of the leukocyte effect. This indicated that the processing method itself influences the platelet quality. By increasing the surface/volume ratio of SDPC, the initial pH of 7.1 was well maintained throughout storage, platelet metabolic rate was slowed, and the function and ultrastructure improved significantly.

In vitro evaluation of a high-efficiency leukocyte adherence filter.

In view of the currently available data, prevention of alloimmunization requires filters with higher efficiency to achieve a reduction in the number of leukocytes below 10 million per transfusion. Two versions (Pall PL-100 and PL-50) of the new generation leukocyte-depletion filters were studied. Single donor (SDPC)- and pooled multiple donor (MDPC) platelets were run in parallel. At a flow rate of 10 ml/min, the PL-100 filter was shown to effectively reduce the number of residual leukocytes to far below the critical immunogenic threshold of 10 million in all SDPC units and in 77% of MDPC units. Apheresis platelets appear not only to be better depleted than pooled multiple donor platelets, but also to have a better post-filtration platelet recovery (96% versus 84%). The efficiency of the smaller version of the filter (Pall-50) was higher than that of the Pall-100 filter for both single and pooled multiple donor platelet concentrates (PC). Leukocytes were absent in more than 92% of units in both types of concentrates. The maximal number of detected leukocytes was 2.2 million in a pool of 6 units. The outcome of filtration of 5-day-old pooled platelets was less favorable than filtration of 1- or 2-day-old pooled platelets, indicating that filtration soon after preparation is preferred to filtration after storage. Post-filtration platelet integrity, activation state, function, and morphology were all well preserved in both single and multiple PCs.

Preparation and storage of "leukocyte-depleted single donor" platelet concentrate: a step forward in effective haemotherapy.

"Leukocyte-depleted" platelet concentrates (LD-SDPC) were prepared by cotton-wool and by polyester filtration of "leukocyte-poor" PC collected by the elutriation technique. The storage characteristics of LD-SDPC were comparable to those of the filtered pools of multiple donor platelet concentrates (LD-MDPC). However, LD-SDPC were less activated and less damaged than LD-MDPC over a 7-day storage period, as evidenced by beta-thromboglobin percent release and lactic dehydrogenase percent leakage in both products. LD-SDPC were prophylactically transfused to 12 thrombocytopenic patients; the mean bleeding time was shortened from 12 min 20 sec to 4 min 39 sec. Corrected count increment (CCI) was 22.8 at 1 hr and 14.1 at 24 hr compared to 15.5 and 10.0, respectively, with standard PCs.