Leukocyte Depletion Filters Research Articles

Detection of cytomegalovirus DNA in peripheral blood of allogeneic bone marrow transplant patients by the nested polymerase chain reaction.

In order to investigate the contribution of transfusion to CMV infection, 20 CMV-seropositive and 3 seronegative patients undergoing allogeneic bone marrow transplantation were studied for their CMV infection. All the patients received cellular blood component transfusion through a leukocyte depletion filter. CMV infection is defined as positive results with a nested double polymerase chain reaction (PCR) and/or IgM antibody testing. Blood samples of 10 healthy marrow donors and 10 pretransplant patients were available for PCR examination. No CMV-DNA was demonstrated. In contrast, among a total of 122 peripheral blood specimens from the 23 posttransplant patients, 51 from 14 patients were positive for CMV-DNA. Of 20 seropositive patients, 15 were transfused with CMV-seronegative blood which is consisted of 14.3% of blood donors and 5 were transfused with CMV-unscreened blood. Four (80%) of the latter 5 seropositive patients showed CMV infection. Of 15 seropositive patients transfused with CMV-seronegative blood, 11 (73.3%) exhibited CMV infection. There was no significant difference in the incidence of CMV infection between the two seropositive patient groups (Fisher's exact probability test). In most cases, CMV infection occurred after 30 days post BMT. Interstitial pneumonia developed in two seropositive patients who had received CMV-seronegative blood products, and had positive results on both PCR and IgM testing. Regardless of transfusing CMV-unscreened or seronegative blood, none of the seronegative patients were infected with CMV. Our present observations suggest that the CMV-seronegative blood component contributes little if any to prevent seropositive patients from CMV infection.

Effect of Filtration on Subsequently Stored Platelet Concentrates

The effect of filtration on the quality of platelet concentrates (PC) during storage was investigated. Two leukocyte depletion filters (Pall PL50HF and Sepacell PL-10A) were applied to filter PC made from a pool of 4 huffy coats. For each experiment 3 PC were pooled and divided into 3 identical PC to eliminate differences between the PC. Two PC were filtered, and the third PC served as an unfil- tered control. A total of 12 experiments was performed. Before filtration, volumes of the PC were 263 ± 11.7 ml (mean±SD). Platelet and leukocyte counts per PC were 241±25.9 x 10^9 and7.2±1.8 x 10^6, respectively. After filtration leukocyte counts did not exceed 5 x 10^4 in any of the PC. In the PC filtered with the Pall PL50HF the mean platelet loss was approximately 14% and with the Sepacell PL-10A, 17%. During a 9-day storage period the pH, PO(2), PCO(2), bicarbonate, lactate and glucose concentration and LDH release as well as the morphology, examined by the swirling effect and microscopically, were not significantly different in filtered and unfiltered units. Filtration through the 2 investigated leukocyte depletion filters for PC did not adversely affect in vitro viability of the platelets during storage.

The present status of blood filtration--fundamentals and the clinical significance of leukocyte depletion and microaggregate filters in blood transfusion

In this review the role of the latest generation of leukodepletion blood filters and the adverse reaction of leukocytes i.e. alloimmunisation, immunosuppression, nonhaemolytic febrile transfusion reaction, platelet refractoriness, transmission of infectious agents are described and discussed. Leukocyte-poor blood component is indicated for patients with a history of nonhaemolytic febrile transfusion reaction, in avoiding alloimmunisation in patients waiting for transplantation or platelet refractoriness and in preventing CMV-infection. In the review the role of microaggregate filters in transfusion complications, namely, nonhaemolytic febrile transfusion reaction, thrombocytopenia, adult respiratory distress syndrome (ARDS), fibronectin depletion and histamine release is evaluated. The need of microfiltration of autologous blood is discussed. It appears that the use of 40 microns microfilters is warranted in a broad array of intensive care settings.

Caractéristiques et modes d'action des filtres à déleucocyter

Since their creation, leukocyte depletion filters, used to prepare leukocyte-poor red cell or platelet concentrates, have been continuously evoluting: their volume has been reduced and their composition has been modified, polyester fibers have replaced cotton wool or cellulose acetate. In the same way, their capacity to remove leukocytes has increased. The mechanisms of cell separation are still unclear. Through published studies, different factors seem to be implicated, such as wetable surface of the filter, surface tension or charge density of fibers. It was also observed that removal of lymphocytes from red cell concentrates is rather based on trapping in the fiber network, and that removal of granulocytes, monocytes and platelets is partly due to activation and subsequent adhesion to the fibers. There have been few studies of the mechanism of leukocytes depletion from platelets concentrates.

Leukocyte depletion filters should be used with apheresis platelets.

Leukocyte depletion filters should be used with apheresis platelets.

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.

Leukocyte depletion filters: A comparison of efficiency

Four commercially available leukocyte depletion filters were evaluated using a flow cytometric technique to determine the efficiency of each type of filter. The Sepacell R-500A and the PALL RC50 were the most efficient in leukocyte depletion having a mean depletion percentage of 99.3% and 99.5%, respectively. The PALL RC100 which is used for two units also had a 99.3% depletion with the first unit but with the second unit the depletion dropped to 94.2%. The imugard IG-500 had a 97.3% depletion. Red cell recovery ranged from 87.4% for the PALL RC50 to 92.2% for the Sepacell R-500A.