Leukocyte reduction of blood components: public policy and new technology

Universal leukodepletion of blood components results in a significant reduction of febrile non-hemolytic but not allergic transfusion reactions

BACKGROUND

Universal leukodepletion of blood components to prevent acute non-hemolytic transfusion reactions (NHTRs) is still a subject of debate.

PATIENTS AND METHODS

Transfusion-associated NHTRs observed at our hospital in the last 6 years were retrospectively analyzed. Buffy-coat depleted red blood cells (bc-RBCs), and if indicated, leucodepleted post-storage (ld-RBCs) were initially used. In April 1997, universal leukodepletion was implemented at our hospital, and thereafter only prestorage ld-RBCs were used. All platelet concentrates transfused during this time were prestorage filtered single-donor apheresis platelets (SDAPs).

RESULTS

A total of 163,090 blood products were transfused from April 1995 to April 2001 (bc-RBC: n=34,040 units; ld-RBC: n=66,967; SDAP: n=14,516; FFP: n=47,567). The number of post-transfusion febrile NHTRs occurring with each blood product was 65 (0.19%) for bc-RBCs, 8 (0.16%) for post-storage ld-RBCs, 16 (0.03%) for prestorage ld-RBCs, 16 (0.11%) for SDAPs, and 10 (0.02%) for FFP. Allergic reactions (n=116) were most frequently observed after SDAP transfusion (0.32%) and occurred at a similarly low rate after transfusion of all other blood components (0.03-0.08%).

CONCLUSION

In conclusion, acute NHTRs rarely occur after the use of leukodepleted blood components. Prestorage appears to be more effective than post-storage leukodepletion in preventing febrile reactions following a blood transfusion.

White blood cell-containing allogeneic blood transfusion, postoperative infection and mortality: a meta-analysis of observational 'before-and-after' studies

BACKGROUND AND OBJECTIVES

An association of white blood cell (WBC) reduction with decreased mortality was reported by one observational, before-and-after study. A meta-analysis was undertaken to examine whether this finding is supported by all the evidence currently available from before-and-after studies, and whether these studies support an association of WBC reduction with a decreased risk of postoperative infection.

MATERIALS AND METHODS

Observational, before-and-after studies were retrieved that reported on postoperative infection and/or mortality between January 1997 and June 2003. Six studies met the criteria for meta-analysis. Unadjusted summary odds ratios (ORs) of postoperative infection or mortality in patients transfused after (compared with before) WBC reduction were calculated across the studies if the hypothesis of homogeneity was not rejected. Adjusted summary ORs were calculated across three studies that had reported multivariate analyses.

RESULTS

There was an unadjusted association of WBC reduction with a decreased risk of postoperative infection [summary OR = 0.93; 95% confidence interval (95% CI), 0.88-0.99; P < 0.01] that did not persist following adjustment for confounding factors (summary OR = 0.94; 95% CI, 0.85-1.04; P > 0.05). There was neither an unadjusted nor an adjusted association of WBC reduction with decreased mortality (summary OR = 0.94; 95% CI, 0.71-1.23; P > 0.05; and OR = 0.92; 95% CI, 0.80-1.05; P > 0.05, respectively).

CONCLUSIONS

An association of WBC reduction with decreased mortality was not detected across the results available from all before-and-after studies. An unadjusted association of WBC reduction with a decreased risk of postoperative infection exists, but this was not detected across the three studies that reported multivariate analyses.

Universal leukoreduction decreases the incidence of febrile nonhemolytic transfusion reactions to RBCs

BACKGROUND

Febrile nonhemolytic transfusion reactions (FNHTR) is a relatively common complication associated with allogeneic transfusion. Because WBCs have been implicated in the mechanism of FNHTRs, it has been proposed that the transfusion of leukoreduced RBCs should be associated with a decreased incidence of FNHTRs. These reactions are generally not life threatening, but they are expensive in their management, evaluation, and associated blood-product wastage. Over the past several years, the proportion of leukoreduced RBCs has increased at Johns Hopkins Hospital in an effort to move toward complete leuko-reduction. A retrospective analysis is reported here of FNHTRs in RBC recipients as the inventory increased in percentage of leukoreduced RBC units.

STUDY DESIGN AND METHODS

Between July 1994 and December 2001, all transfusion reactions (TRs) associated with the transfusion of allogeneic RBCs were retrospectively analyzed. Both computerized data and individual TR reports were reviewed. Patients who had both allergic and febrile features were included as part of both categories. TRs were reported as a percentage of total units transfused. Two time periods were selected for direct comparison. July to December 1994 represents the time period before the initiation of an increase in leuko-reduction. July to December 2001 represents a time period when almost complete leukoreduction (99.5%) had been achieved. The TR data were compared between these two time periods, comparing a time before leuko-reduction to a time period after leukoreduction had been achieved. The trends in TRs over the entire 7.5-year period of July 1994 to December 2001 were also assessed.

RESULTS

In the initial period before the initiative to move toward leukoreduction, 96 percent of our RBC inventory was non-leukoreduced. In the study period after leukoreduction, 99.5 percent of our RBC inventory was leukoreduced. When comparing these two time periods, the incidence of FNHTRs decreased from 0.37 percent to 0.19 percent (p = 0.0008). The trend over the entire 7.5-year study period confirms the decrease in FNHTRs as the percentage of leukoreduced RBCs increased. The incidence of allergic TRs has remained unchanged over this time period.

CONCLUSIONS

As our institution has increased its inventory of leukoreduced RBCs to approximately 100 percent, selective leukoreduced protocols have been discontinued. The incidence of FNHTRs has decreased significantly and the rate of allergic reactions has essentially remained unchanged. Leukoreduction is effective in decreasing FNHTRs associated with the transfusion of allogeneic RBCs.

Increasing oxygen tension improves filtration of sickle trait donor blood

A major cause of filter failure of red cell (RBC) components from donors with sickle cell trait (HbAS) is the polymerization of haemoglobin. The oxygen saturation (sO2) of blood stored in various plastics and different volumes of air was assessed. Blood from 10 HbAS donors was collected and divided into two bags, one with air added, one without. Bags with added air had increased sO2 levels (from 49 +/- 10% to 76 +/- 6%). Filtration was successful for nine of 10 components with air, and one of 10 without air. Successful filtration of RBC components occurs when sO2 is increased.

Filtration induces changes in activity states and leucocyte populations

The distribution of leucocyte subpopulations in platelet concentrates (PC) derived from pre-storage filtered platelet-rich plasma (PRP), the cell suspension obtained by reverse filter washing and the post-filtered PC, were monitored by immunophenotyping analysis using CD3, CD20 and CD33. Leucocyte activation analysis with the CD11b marker revealed that this molecule is up regulated in neutrophils taken from the filter. This, together with the loss of cell viability during the enrichment process, suggests that contact with the filter matrix and processing and storage of samples containing leucocytes may lead to activation and loss of leucocyte viability. These changes were found to be more pronounced in less stable myeloid cells and account for the differences reported among various authors which in some cases related to operational conditions such as the enrichment process used and the length of time between filtration and analysis of samples. Finally, statistical analysis of the results obtained by immunophenotypic studies indicate that post-filter samples (S) contain significantly higher numbers of CD33+ myeloid cells when compared to (PF) the pre-filter samples (65.03%+/-12.6 and 24.56%+/-14.73, p<0.0000), with a decrease in T cells (50.72%+/-14.80 in PF and 24.05+/-9.48 in the cell suspension (S), p<0.0007) and B cells (14.96+/-9.31 in PF and 9.9+/-5.22 in S, p<0.201). A new strategy for assessing the influence of the filtration process on residual leucocyte activation and viability is described. This has direct relevance to collection, processing, storage and quality monitoring of PC.

The effect of exposing murine splenocytes to UVB light, psoralen plus UVA light, or gamma-irradiation on in vitro and in vivo immune responses

BACKGROUND

WBCs in blood components are a major factor contributing to immune responses such as GVHD and alloimmunization that follow transfusion. Irradiation of blood components has been used to regulate the contribution of donor WBCs to these immune responses. A systematic comparison of how the exposure of lymphoid cells to gamma-irradiation, UVB light, or psoralen + UVA light (PUVA) effects immune response was conducted to better define the best type of irradiation to be used in different clinical settings.

STUDY DESIGN AND METHODS

Murine spleen cells were irradiated with varying doses and tested for their in vitro ability to be activated, to proliferate in response to mitogen or allogeneic stimulator cells, or to serve as stimulator cells. Irradiated donor cells were also tested for in vivo generation of GVHD, induction of alloantibody production, induction of restricted cytolytic T lymphocytes, and persistence of irradiated cells.

RESULTS

In general, increasing amounts of irradiation resulted in increased inhibition of in vitro and in vivo responses, although the doses required for inhibition differed from assay to assay. In contrast, irradiation of donor cells did not always result in inhibition of recipient alloantibody responses but was dependent on the donor-recipient combination that was studied.

CONCLUSION

Control of the in vivo outcomes of transfusing allogeneic cells is regulated by the type and dose of irradiation used and by the genotype of the donor and/or recipient.

Absence of HBV and HCV, HTLV-I and -II, and human herpes virus-8 activation after allogeneic RBC transfusion in patients with advanced HIV-1 infection

BACKGROUND

The Viral Activation Transfusion Study was a prospective, randomized, double-blind comparison of transfusion with WBC-reduced versus non-WBC-reduced RBCs to HIV+ patients. The primary study characterized the effect of transfusion on HIV and CMV activation by monitoring viral load changes. The present study analyzed HBV, HCV, HTLV-I and -II, and human herpes virus-8 (HHV-8) viral load before and after transfusion to evaluate the further hypothesis that global immune stimulation following allogeneic RBC transfusion results in activation and increased viral proliferation of chronic viral infections other than HIV and CMV.

STUDY DESIGN AND METHODS

Baseline samples from 519 to 523 subjects were screened for HBV, HCV, HTLV-I and -II, and HHV-8 infection, and baseline, serial weekly, and quarterly blood samples from infected subjects in the non-WBC-reduced arm were evaluated for changes from baseline in viral nucleic acid and ALT levels.

RESULTS

Seroprevalence of HBV, HCV, HTLV-I and -II, and HHV-8 was 68, 25, 5, and 30 percent, respectively. No significant induction of HBV, HCV, HHV-8, or HTLV-I and -II viral replication following allogeneic transfusion of non-WBC-reduced blood was observed. A significant, albeit small, association was observed between transfusion and ALT.

CONCLUSIONS

Based on these results and our previous finding that no adverse effect on HIV and CMV viral load and disease progression results from allogeneic transfusion, no evidence is found to support the selective use of WBC-reduced blood components for HIV-infected patients.

Residual WBC subsets in filtered prestorage RBCs

BACKGROUND

New-generation RBC filters reduce WBC concentrations by 4 to 5 logs and may prevent or decrease transfusion complications such as HLA alloimmunization, nonhemolytic febrile reaction, and transfusion-transmitted infections. The residual level of WBC subsets may influence efficacy of WBC reduction for preventing various complications. This study analyzed subsets of residual WBCs in WBC-reduced RBC components prepared for a large, multicenter prospective study.

STUDY DESIGN AND METHODS

The Viral Activation Transfusion Study (VATS) assessed the impact of WBC reduction in HIV-1-infected patients undergoing RBC transfusion. WBC-reduced RBC from 11 clinical sites with variable filtration practices were sorted into "low,""middle," and "high" groups based on residual WBC concentration. Subsets were isolated from units by immunocapture (anti-CD4-, anti-CD8-, anti-CD15-, and anti-CD19-coated magnetic beads) and quantified by PCR amplification.

RESULTS

After validation studies confirming test methodology, 105 VATS WBC-reduced RBC samples were analyzed. Concentrations of subsets in low and middle residual WBC groups were very low in contrast to relatively high concentrations in the high group. Although highly significant differences were identified between the middle and high groups for total WBCs and all subsets, no single subset predominated.

CONCLUSION

These results suggest that overall efficacy of WBC filtration correlates with removal of WBC subsets.

Sickle Hb polymerization in RBC components from donors with sickle cell trait prevents effective WBC reduction by filtration

BACKGROUND

RBC components collected from donors with sickle cell trait frequently occlude WBC-reduction filters. In vitro, sickle trait RBCs have the potential for sickle Hb (Hb S) polymerization at low oxygen saturations and high Hb concentrations.

STUDY DESIGN AND METHOD

To determine if the low pH and high osmolarity of the CP2D used in the collection contributed to filter failures, the filterability of sickle trait donor RBCs collected in CP2D was compared with RBCs from the same donors collected in heparin.

RESULTS

Five of six sickle trait components collected in CP2D did not complete filtration, but all six RBC components collected in heparin filtered completely. RBC components collected in CP2D from four other sickle trait donors were divided in two, and one-half was treated with carbon monoxide to convert Hb S to its liganded form to prevent Hb S polymerization. All four carbon monoxide-treated components filtered within 9 minutes, but only one untreated component filtered completely. RBC components collected by apheresis contained less CP2D, and five of seven sickle trait apheresis components filtered completely; four of the five filtered rapidly (<15 min) and one filtered in 100 minutes. Hb oxygen saturation was greater in the four rapidly filtering apheresis RBC components (68 +/- 9%) than in the three that filtered slowly or incompletely (37 +/- 5%, p = 0.03).

CONCLUSIONS

Hb S polymerization appears responsible for RBC WBC-reduction filter failures. Citrate anticoagulant and low oxygen saturation are responsible in part for Hb S polymerization in this setting.

Inhibition of murine GVHD by PEN110 treatment

BACKGROUND

The presence of WBCs in blood components is the primary factor influencing the immunologic consequences of transfusion, such as GVHD and alloimmunization. Depletion or inactivation of WBCs can reduce the deleterious responses. Because treatment with PEN110 (Inactine, V. I. Technologies), an ethyleneimine derivative that disrupts nucleic acid replication, was shown to inactivate in vitro human PBMNC function, the ability of PEN110-treated cells to trigger GVHD or alloantibodies was studied with in vivo murine models.

STUDY DESIGN AND METHODS

In vitro assays were employed to confirm that PEN110 treatment inactivated murine splenocyte function as effectively as for human PBMNCs. In vivo experiments in mice examined the ability of PEN110-treated cells to induce GVHD responses in a parent into F1 hybrid GVHD model, to induce alloantibodies, to stimulate MHC-restricted cytolytic T lymphocyte responses, and to persist after injection.

RESULTS

PEN110-treated murine splenocytes did not respond or induce responses in any in vitro or in vivo assay. The PEN110-treated cells were eliminated from blood and secondary lymphoid organs much more rapidly than were untreated cells.

CONCLUSION

PEN110 treatment prevents the development of GVHD and alloantibody production following WBC transfusion in a murine model system, supporting the continued development of PEN110 treatment of cellular blood components as an alternative to gamma irradiation for the prevention of GVHD.

PEN110 treatment functionally inactivates the PBMNCs present in RBC units: comparison to the effects of exposure to gamma irradiation

BACKGROUND

The presence of WBCs in blood components is the major factor influencing the immunologic consequences of transfusion. Attempts to ameliorate these responses have used WBC reduction or inactivation by ionizing radiation. PEN110 (Inactine, V. I. Technologies) is a chemical that inhibits the replication of infectious pathogens by modifying their nucleic acids. These experiments compared effects of PEN110 treatment or gamma irradiation on WBC function.

STUDY DESIGN AND METHODS

Aliquots of non-WBC-reduced RBC units were treated with PEN110 or gamma irradiation with appropriate controls, and PBMNCs from these units were tested with in vitro assays. The assays included immunophenotyping, activating T cells with phorbol ester, proliferation of cells in response to mitogens or allogeneic cells, and determining the ability of cells to stimulate proliferative responses and to produce IL-8. DNA fragmentation following PEN110 treatment was examined by PCR and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end labeling assays.

RESULTS

Treatment of non-WBC-reduced RBC units with PEN110 functionally inactivated WBC in all in vitro assays used. In contrast, while gamma irradiation inhibited proliferation of the WBCs, it did not or only partially inhibited the ability of WBC to function in the other assays. PEN110, but not gamma irradiation, rapidly induced fragmentation of cellular DNA.

CONCLUSION

Because PEN110 was as effective as gamma irradiation at inhibiting WBC proliferation, PEN110 treatment could potentially be used to prevent the development of GVHD following transfusion.

Inline-filtration

BACKGROUND

Routine leukocyte-depletion (LD) of cellular blood products, and even plasma, is currently being implemented in most European countries, as a result of the fear that the variant Creutzfeldt-Jakob-disease (vCJD) might be transmissible by transfusion. However, not only is the scientific evidence supporting such a notion scarce, but the benefits of applying this procedure to all patients also remain unfounded.

METHODS

A MEDLINE-research for studies dealing with the indications for LD was performed. In addition, the guidelines and recommendations of national and international health authorities were scrutinized.

RESULTS

To date,the only proven benefit of LD that can be applied to all patients is the reduction of non-hemolytic febrile transfusion reactions. In addition, LD reduces HLA-immunization and platelet refractoriness in multi-transfused patients. In immunocompromized patients, LD reduces transfusion-transmitted CMV-disease. Furthermore, a minority of 5-10% of transfusion-related-acute-lung-injury cases can be prevented by LD. However, the potential of reducing the immunomodulating effects of transfusion such as postoperative infection, cancer-recurrence-related or overall mortality and of reducing septicemia due to bacterial contamination is still at issue. AIDS patients do not benefit from LD, at least. The suitability of LD for preventing the transmission of vCJD is at best hypothetical. Potential risks of LD like increased leakages have not been taken into account adequately to date.

CONCLUSIONS

At present, the scientific evidence does not justify the introduction of LD as a routine measure. In times of limited health care resources, this costly procedure might limit access to medical services with proven effectiveness and efficiency. In addition, the loss of 5-10% of the red cell pool is predicted to lead to more blood supply shortages than previously seen.

A prospective, randomized clinical trial of universal WBC reduction

BACKGROUND

Recipient exposure to allogeneic donor WBCs results in transfusion complications for selected populations of recipients. Whether or not WBC reduction should be universally applied is highly controversial.

STUDY DESIGN AND METHODS

In a general hospital, a randomized, controlled clinical trial of conversion to universal WBC reduction was conducted. Patients (11%) with established medical indications for WBC-reduced blood were not eligible. All other patients who required transfusion were assigned at random to receive either unmodified blood components or stored WBC-reduced RBCs and platelets. Analysis for each patient was restricted to the first hospitalization.

RESULTS

All eligible patients (n = 2780) were enrolled. Three specified primary outcome measures were not different between the two groups: 1) in-hospital mortality (8.5% control; 9.0% WBC-reduced; OR, 0.94 [95% CI, 0.72-1.22]; p = 0.64); 2) hospital length of stay (LOS) after transfusion (median number of days, 6.4 for control and 6.3 for WBC-reduced; p = 0.21); and 3) total hospital costs (median, $19,500 for control and $19,200 for WBC-reduced, p = 0.24). Secondary outcomes (intensive care LOS, postoperative LOS, antibiotic usage, and readmission rate) were not different between the two groups. Subgroup analysis based on patient age, sex, amount of blood transfused, or category of surgical procedure showed no effect of WBC reduction. Patients who received WBC-reduced blood had a lower incidence of febrile reactions (p = 0.06).

CONCLUSION

A beneficial effect of conversion from selective to universal WBC reduction was not demonstrated.

Applying a novel statistical process control model to platelet quality monitoring

BACKGROUND

Many countries are implementing universal WBC reduction of blood components Thus, manufacturing procedures must include QC techniques to detect units that fail to meet established standards.

STUDY DESIGN AND METHODS

A statistical process control model, based on the exponentially weighted moving average of the cumulative distribution function (CDF-EWMA), was developed to detect shifts in a mean and/or variance of a process. The model's parameters (weights) were optimized to maximize detection of an out-of-control process while minimizing sensitivity to autocorrelation. Validation was performed using a retrospective set of WBC-reduction data obtained from a blood bank. The WBC-reduction process was considered in control when there was 95-percent confidence that more than 95 percent of platelet concentrates would contain less than 1 x 10(6) WBCs (6.0 log WBC) as required by European standards. A sentry setting of 5.7 log WBCs was used to allow earlier detection of an out-of-control process.

RESULTS

Graphic output of the CDF-EWMA model provided a continuous update of the probability that a WBC-reduction process was in control. Using the validation data, the model showed that the process was in control until Observation 332, at which point residual WBCs per unit increased. However, the first platelet concentrate to exceed specified criteria (Observation 346) occurred after the model detected that the process was out of control, demonstrating the forecasting value of this model. This deviation corresponded to an equipment failure in a single apheresis instrument. The Shewhart and EWMA techniques were similarly able to detect when the process was out of control using the test data.

CONCLUSION

As a statistical process control model, the CDF-EWMA provides real-time estimation of the fraction of components meeting a regulatory limit. It is capable of detecting developing QC problems before units fail to meet regulatory requirements and is a potential alternative to other QC techniques for monitoring WBC reduction of blood components.

Limited efficacy of universal leucodepletion in reducing the incidence of febrile nonhaemolytic reactions in red cell transfusions

This article demonstrates a 62% reduction in the number of febrile nonhaemolytic transfusion reactions (FNHTRs) and 50% reduction in febrile reaction rate associated with red cell transfusions following graded introduction of universal leucodepletion. Though this is a statistically significant reduction (P = 0.009), it shows limited efficacy in abrogating this complication. We also found a reduction in the proportion of cases of FNHTRs with lymphocytotoxic antibodies over the period studied from 54% in 1998, 28% in 1999 to 23% in 2000. This corresponds to a relative increase in the number of febrile reactions without human leucocyte antigen (HLA) antibodies following full implementation of universal leucodepletion, as the total number of reported reactions actually fell considerably during the period. The increase in the number of cases without HLA antibodies was directly proportional to the increase in the number of leucodepleted units used.

Bacterial contamination of blood products: factors, options, and insights

Transfusion of bacterially contaminated blood products remains an overlooked problem. However, the risk of receiving a bacterially contaminated unit is greater than the combined risk of HIV-1/2, HCV, HBV, and HTLV I/II [American Association of Blood Banks Bulletin, no. 294, 1996]. Topics covered in this article include: the current incidence, clinical presentation and outcome, effective methods of detection, and ways to reduce bacterial contamination of blood products. There is no one existing strategy that can completely eliminate the risk of bacterial contamination. It is inevitable that partial solutions or combinations of methods will be implemented in the near future.

Signs and symptoms associated with the transfusion of WBC-reduced RBCs and non-WBC-reduced RBCs in patients with anemia and HIV infection: results from the Viral Activation Transfusion Study

BACKGROUND

RBC transfusion is associated with fever and other reactions in some patients. The Viral Activation Transfusion Study randomly assigned patients to receive either unmodified or WBC-reduced RBCs and thus offered an opportunity to assess the effect of WBC-reduced RBCs on the incidence of transfusion reactions prospectively.

STUDY DESIGN AND METHODS

This prospective, randomized, double-blind, multicenter study compared prestorage WBC-reduced RBCs to unmodified RBCs in HIV-infected, CMV-seropositive, and transfusion-naive persons who required transfusions for anemia. Primary endpoints were survival and change in the plasma HIV RNA level at 7 days after transfusion. The incidence of transfusion reactions was prospectively evaluated.

RESULTS

The two groups had similar baseline characteristics and study endpoints; 3864 RBC units (median storage age, 9 days) were administered to 531 patients during 1745 transfusions. The most frequent signs reported were elevated temperature and hypotension. Subjects who reported fever within the week prior to transfusion were more likely to have an elevation in temperature associated with transfusion. The administration of RBCs that were less than 10 days old was associated with a marginal increase in the incidence of transfusion-associated temperature elevation among recipients of unmodified RBCs, but not among recipients of WBC-reduced RBCs. Caregivers reported fewer instances of both elevated temperature and hypotension than were identified by review of transfusion records.

CONCLUSIONS

The incidence of elevated temperature and hypotension associated with transfusion in this population was unexpectedly high. Use of WBC-reduced RBCs had no effect on the overall rates of elevated temperature or hypotension associated with transfusion of RBCs. The occurrence of a pre-existing fever was associated with a higher frequency of transfusion-associated elevated temperature.

Quantitation of residual WBCs in filtered blood components by high-throughput, real-time kinetic PCR

BACKGROUND

The effort to eliminate transfusion complications associated with WBCs has led to the widespread use of filters able to reduce WBC concentrations to <or=0.1 WBC per microL blood. This has necessitated sensitive QC methods to quantitate residual WBCs in filtered units. One fast, effective method is DNA amplification using real-time kinetic PCR (kPCR).

STUDY DESIGN AND METHODS

Two methods of preparation of standards were compared and used for the optimization of quantitative kPCR. The first involved spiking genomic DNA cell lysate into a diluent, followed by a series of 1 in 10 dilutions. The second involved spiking serial 1 in 10 dilutions of WBCs into twice-filtered fresh whole blood. Two hundred fifty filtered frozen whole-blood samples were amplified in duplicate to show the kPCR assay's reproducibility. Another 359 filtered frozen whole blood samples were used to compare data from kPCR with data from a standard PCR protocol using (32)P-labeled probe and autoradiography. All specimens were amplified for conserved HLA DQ(alpha) sequences.

RESULTS

Standards prepared by both methods gave reproducible and equivalent results. Quantitation of standards representing a dynamic range of 8 x 10(o) to 8 x 10(5) WBCs per mL, yielded standard deviations ranging from 0.59 cycle to 1.04 cycles (a one-cycle increase is equivalent to a twofold increase in WBC concentration). The scatter graph of the 250 samples tested in duplicate by kPCR generated a slope of 1.0122 and an R(2) value of 0.9265. The comparison of kPCR and (32)P-probe hybridization results on 359 clinical samples gave a scatter-graph slope of 0.9428 and an R(2) value of 0.8718, indicating excellent agreement of the methods over a 4-log dynamic range.

CONCLUSION

kPCR is a high-throughput, sensitive assay that could prove useful in routine quality assurance of the WBC reduction process.

Improved storage of erythrocytes by prior leukodepletion: flow cytometric evaluation of stored erythrocytes

In vivo phagocytosis of senescent red blood cells (RBCs) by macrophages occurs 120 days after their release into the circulation. It depends on two sequential signals that trigger phagocytosis: (1) desialylation of membrane glycoconjugates with the exposure of the penultimate beta-galactosyl residues and (2) exposure of phosphatidylserine in the membrane outer leaflet. Leukodepleted and nonleukodepleted RBCs were compared using flow cytometric procedures to determine whether the in vitro deterioration of RBCs during storage might be attributable to an identical mechanism of desialylation induced by leukocyte neuraminidases, resulting in exposure of beta-galactosyl and subsequently phosphatidylserine residues - signals of senescent RBCs. Without prior leukodepletion, stored RBCs showed an increased population of senescent RBCs (using light scatter measurements), extensive desialylation with the exposure of beta-galactosyl residues (using specific fluorescein isothiocyanate [FITC]-lectins), significant exposure of phosphatidylserine in the outer leaflet of the RBC membrane (using FITC-annexin V), and extensive in vitro phagocytosis (using PKH-26-labeled RBCs). There were minimal changes observed with the leukodepleted RBCs. These results lead to the conclusion that leukocyte enzymes, including neuraminidases, are definitive contributers to the desialylation of RBCs during storage and to the exposure of phosphatidylserine residues. These deleterious effects resulting from highly active leukocyte enzymes are preventable by prior leukodepletion of the stored RBCs. Previously developed flow cytometric procedures to detect in vivo "RBC senescence" have been applied and proved to be reliable criteria to monitor the viability of stored RBCs.

WBC reduction in RBC concentrates by prestorage filtration: multicenter experience

BACKGROUND

As universal leukocyte (WBC) reduction (ULR) is being considered as a new standard, few data are available on the performance of WBC-reduction filtration in routine practice. The performance of WBC-reduction in RBCs, using varied filtration practices, in meeting the current FDA requirement (<5 x 10(6)), Council of Europe (EC) recommendation, the proposed FDA requirement (<1 x 10(6)), and a more stringent proposal (<5 x 10(5)) for residual WBCs per RBC unit was assessed and compared.

STUDY DESIGN AND METHODS

Participating facilities were the 11 sites of the Viral Activation Transfusion Study (VATS), a prospective study of the impact of transfusion with and without WBC-reduction on survival and HIV viral load in HIV-1-infected patients. Patients randomly assigned to undergo WBC reduction were required to receive RBCs < or =14 days old that had undergone prestorage (within 72 hours of collection) WBC-reduction filtration by a method devised to achieve a postfiltration WBC count of <5 x 10(6). Residual WBC quantitation was performed by PCR in the central VATS laboratory by using frozen WBC-reduced RBC samples obtained at issue for transfusion.

RESULTS

A total of 1869 WBC-reduced RBC units were studied. Filtration practices varied within and between sites. There were significant differences in mean residual WBC counts at the 11 sites (p<0.001). Among the WBC-reduced RBC units, 0.8 percent exceeded 5 x 10(6) WBCs per unit, 8.3 percent exceeded 1 x 10(6) WBCs per unit, and 14.3 percent exceeded 5 x 10(5) WBCs per unit.

CONCLUSION

Residual WBCs in WBC-reduced RBC units vary within and between sites. WBC reduction was successful, in that over 99 percent and 91 percent of VATS WBC-reduced RBC units met US and EC thresholds, respectively. However, the small but measurable failure rate indicates that not every unit will meet these guidelines.

Prestorage universal WBC reduction of RBC units does not affect the incidence of transfusion reactions

BACKGROUND

Febrile nonhemolytic transfusion reaction (FNHTR) has been identified as a pivotal reason for prestorage universal WBC reduction. A regional blood center implemented universal prestorage WBC reduction for RBCs on January 1, 2000. Whether prestorage universal WBC reduction of RBC units will affect FNHTR is not known.

STUDY DESIGN AND METHODS

All reports of RBC transfusion reactions at Barnes-Jewish Hospital submitted for evaluation to the blood bank, before and after the implementation of WBC reduction of RBCs, were retrospectively evaluated.

RESULTS

For the 36,303 allogeneic RBC transfusions administered in 1999, 85 reactions (0.23%) were reported. These reactions were classified as FNHTR in 43 cases, allergic in 13, delayed hemolytic in 19, and miscellaneous in 10. For the 31,543 non-WBC-reduced RBC transfusions performed in 1999, 78 reactions (0.25%) were reported. These reactions were classified as FNHTR in 39 cases, allergic in 13, delayed hemolytic in 19, and miscellaneous in 7. In the first half of 2000, 32 reactions (0.20%) were reported for 16,093 prestorage WBC-reduced RBC transfusions (p = 0.41). There were 13 FNHTRs and 10 allergic, 7 delayed hemolytic, and 2 miscellaneous reactions. The use of prestorage WBC-reduced RBCs did not significantly affect the rate of reactions classified as allergic (0.04% in 1999; 0.06% in 2000; p = 0.43) or as FNHTR (0.12% in 1999; 0.08% in 2000; p = 0.33). For all patients, universal WBC reduction in 2000 did not reduce the rate of FNHTR from the rate seen with selective bedside WBC reduction, the practice used in 1999 (0.12% in 1999; 0.08% in 2000; p = 0.36).

CONCLUSION

No significant difference was found in the incidence of transfusion reactions in patients receiving prestorage WBC-reduced RBCs and non-WBC-reduced RBCs. In addition, no difference was found in transfusion reaction rates when periods of prestorage universal WBC reduction were compared to those of selective WBC reduction.

Number of RBC units and rate of transfusionto anemic HIV-positive patients assigned to receiveWBC-reduced or non-WBC-reduced RBCs: the viral activation transfusion study experience

BACKGROUND

It is known that the use of filtration to reduce WBCs in RBC units is associated with a 6- to 15-percent loss of RBCs. It is not known if the use of such WBC-reduced RBCs results in an increased need for RBC units or in the transfusion of more units per year to patients with anemia.

STUDY DESIGN AND METHODS

In the multicenter Viral Activation Transfusion Study (VATS), anemic HIV-positive patients were randomly assigned to receive either WBC-reduced or non-WBC-reduced RBCs. The number of RBC units transfused per patient and the rate of RBC use were studied. All RBC units given after the enrollment transfusion were counted, until the end of follow-up or the occurrence of bleeding (receiving >5 RBCs within 2 consecutive days).

RESULTS

As expected, the WBC-reduced RBC units in VATS were lighter in weight than the non-WBC-reduced units (median weight: WBC-reduced, 300 g; non-WBC-reduced, 330 g; p<0.0001). After the enrollment transfusion, 258 WBC-reduced arm patients received 1279 units of RBCs (average, 5.0 units/patient, median, 2 units) while 262 patients in the non-WBC-reduced arm received 1111 RBCs (4.2 units/patient; median, 2 units). The number of units transfused for anemia was slightly greater in the WBC-reduced arm, but the difference was not significant (p = 0.41). Similarly, the rate of RBC use was somewhat higher in the WBC-reduced arm, but the difference was not significant (p = 0.14). The median was 2.3 units per patient per year of follow-up in the WBC-reduced arm; the median in the non-WBC-reduced arm was 1.2 units.

CONCLUSION

This study confirms that WBC-reduced RBC units are significantly lighter in weight than non-WBC-reduced RBCs. However, in the setting of a large, randomized, blinded study of transfusion for anemia, the smaller size of the WBC-reduced RBC units had no significant effect on the number of RBC units transfused or on the rate at which RBC units were used. In this study, the frequency of blood transfusion may have had a greater relationship to the frequency of routine, scheduled appointments or transfusion orders for a specified Hb trigger than to the actual Hb content of the unit.

Universal leukocyte reduction

Leukocyte reduction of blood components, in the United States, is generally reserved for conditions in which a clinical indication has been documented. There is no evidence that either Creutzfeldt-Jakob disease or variant Creutzfeldt-Jakob disease are transmitted by transfusion in humans or that leukocyte reduction of blood components could reduce their transmission. A number of adverse outcomes following transfusion are alleged to be the result of white blood cells. At this point in time, there are insufficient clinical data to justify the universal leukocyte reduction of blood components.

Cost-effectiveness analysis and the selection of blood products

A new generation of blood components and transfusion modalities aimed at further reducing real or hypothetical risks threatening the blood supply is available. Since the risk of infection with transfusion-transmitted viruses is already very low, many of these new interventions provide a minimal health benefit at a very high cost. It is even possible that risks inherent to the new technologies themselves could surpass the current risk of transfusion-transmitted viruses. For some of the new blood components, such as leukoreduced products, the poor cost-effectiveness projections may be substantially improved if the purported health benefits are eventually proved in appropriate randomized, controlled clinical trials. Meanwhile, cost-effectiveness analyses show that allocating more resources to improve the safety of donated blood may actually decrease the overall transfusion safety by subtracting resources from other areas of the health care system, so a realignment of costs with health benefits seems necessary.

Prions and blood products

The transmission of Creutzfeldt-Jakob disease (CJD) by human pituitary-derived growth hormone has led to concerns that blood products might also provide a route for the iatrogenic transmission of CJD. A number of actions have been implemented by regulatory authorities to address such concerns, and numerous studies have been undertaken to determine whether or not there is a risk of CJD being transmitted in this manner. To date, no excess risk has been identified, leading to a growing consensus that there is little or no risk of long established forms of CJD being transmitted to recipients of blood products. This opinion does not extend to new variant CJD (vCJD) which is found predominantly in the UK and is believed to have resulted from the transmission of bovine spongiform encephalopathy (BSE) to humans. Unlike that of CJD, the prevalence of vCJD is not known. In addition, the detection of abnormal prion protein in the tonsils of vCJD-infected individuals has led to speculation that blood infectivity may be greater than in patients with CJD. A number of precautionary measures have been taken to address the possibility that vCJD may be transmissible by blood products; however, further scientific advances are needed to enable this risk to be defined. A suitable screening test is required to identify any infected blood donors, particularly where cellular blood components are being derived from populations believed to be at risk from BSE infection. Recent experimental data suggest that process operations used in the manufacture of plasma products may be capable of removing prion agents to a significant extent. However, further work is required to confirm these observations and to determine whether or not all potential vCJD infectivity would be removed by these means.