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Answers to Frequently Asked Questions About Using Leukocyte Reduction Filters

Leukocyte reduction of blood has become an increasingly important part of transfusion medicine over the past several years. As technological advances are made in product performance and handling, questions arise regarding the various filters available for use during blood component processing in the hospital laboratory, as well as during administration of blood at the bedside. This booklet is intended to address these most frequently asked questions, as well as to provide a resource to understanding Pall Medical’s Purecell® High Efficiency Leukocyte Reduction Filters and Leukocyte Blood Processing Filtration Systems. Filtration At the Hospital Bedside Filtration In the Hospital Laboratory

Question 1: Why leukocyte reduce blood components?

Answer:
Leukocytes are unnecessary contaminants in unfiltered blood products and have been reported to be responsible for a variety of adverse reactions, including:
  • Alloimmunization, which may lead to platelet refractoriness if multiple and/or subsequent transfusions are required1
  • Febrile non-hemolytic transfusion reactions (FNHTR)2
  • Immunosuppression 3,4 which may contribute to an increased incidence of postoperative infections5,6 and tumor recurrence7,8
  • Transmission or reactivation of intracellular viruses (i.e., cytomegalovirus [CMV] and human T-cell lymphotropic virus type I [HTLV-I])9,10 The increased incidence of morbidity, as well as the high costs associated with transfusion complications has led to the development of filters to reduce leukocytes in cellular blood components. Leukocyte reduction has been demonstrated to be clinically effective in reducing the incidence of these transfusion-related complications, including post operative infections5,6 which can significantly decrease the cost of medical care4,11,12 for these patients, producing significant cost reduction to hospitals annually. Today leukocyte reduction may be easily accomplished in any hospital situation.

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Question 2: What is the micron rating of a Pall Leukocyte Reduction Filter?

Answer:
Leukocyte reduction filters are not micron rated. They are rated on the efficiency of leukocyte reduction13. The efficiency claims for Pall Purecell® High Efficiency Leukocyte Reduction filters are based on performance data using average leukocyte residual counts. Filtration is based on a number of mechanisms, including adsorption of the leukocytes to the filtration media. In contrast, the Pall SQ40S microaggregate filters for blood transfusion are 40 micron rated. Pall microaggregate filters are a screen type filter, and filtration is based on direct interception to retain particles and microaggregates. Pall microaggregate filters are indicated for the transfusion of stored blood, packed red cells, platelet and granulocyte concentrates, and ViaSpan®, an organ flushing and storage solution*.

Although Pall SQ40S filters retain microaggregates that consist of nonviable leukocytes, they do not achieve the low residual levels possible with Pall leukocyte reduction filters. Pall Purecell® High Efficiency Leukocyte Reduction filters for red blood cell or platelet transfusion should be used when leukocyte reduction is the goal at the bedside.

Pall’s Leukotrap® in-line filtration systems are available for use in the hospital blood bank or regional blood center.

* ViaSpan is a registered trademark of DuPont Merck Pharmaceutical Co.


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Question 3: Can I filter red blood cell components through a leukocyte reduction filter for platelets and/or platelet components through a leukocyte reduction filter for red blood cells?

Answer:
Leukocyte reduction filters are designed to be used with a specific blood component and must be used for indications listed on the product label. For instance, platelet filters must be used for the filtration of platelets, and red blood cell filters must be used for the filtration of red blood cells (or whole blood).

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Question 4: Is all leukocyte filtration technology the same?

Answer:
Leukocyte reduction filters differ from manufacturer to manufacturer in white blood cell reduction efficiency, performance and consistency. In addition, different leukocyte reduction technologies produce different residual white blood cell subsets and biochemical end products14. Pall Purecell® High Efficiency Leukocyte Reduction filters and Leukotrap® systems have been clinically demonstrated to produce a highly specific blood product that dependably and consistently provides the lowest residual leukocyte levels. These differences separate Pall technology from other manufacturers. Pall filtration technology has been the choice of researchers in most of the milestone clinical studies published on leukocyte reduction.

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Question 5: Are leukocyte reduction filters available for pediatric patients?

Answer:
Yes. Pall Medical offers products for both neonatal and pediatric transfusions (Purecell® NEO and the Purecell® PL1, respectively). See Table 1 for the product that best suits your needs.

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Question 6: Where and when should blood components be leukocyte reduced?

Answer:
Filtration may take place at the patient’s bedside, in the hospital laboratory, or blood center. Decisions about when and where to leukoreduce are based on cost considerations, convenience, patient benefits, and other factors. Considerations in selecting laboratory or bedside filtration are included in Table 2.13

Regardless of which method is selected, Pall Medical offers the broadest array of products to meet the needs of both the hospital and blood center customer. Our line of Purecell® High Efficiency Leukocyte Reduction Filters for the hospital customer and Leukotrap® Systems for the Blood Center provide solutions to the high costs associated with leukocyte associated transfusion complications.


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Question 7: Do I need an additional blood filter (clot screen or microaggregate filter) when I am using a leukocyte reduction filter at the bedside?

Answer:
No. Leukocyte reduction filters also retain microaggregates, which eliminates the need for a separate standard clot screen or microaggregate filter when blood components are administered and leukocyte reduced at the bedside.

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Question 8: If a blood component has been leukocyte reduced in the laboratory, must it be transfused through a clot screen or microaggregate filter at the bedside?

Answer:
Yes. Blood components that are leukocyte reduced in the laboratory must be transfused through a blood administration set containing a standard (170-micron) clot screen, in order to remove blood clots and other debris15.

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Question 9: How many units of blood can be administered through a Pall Purecell® High Efficiency Leukocyte Reduction Filter?

Answer:
Pall Medical’s array of leukocyte reduction filters are designed for specific quantities of blood components.

Table 1 identifies a variety of options to suit the needs of the hospital transfusion service or health professional at the bedside.


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Question 10: How long can a leukocyte reduction filter remain in use?

Answer:
Leukocyte reduction filters are designed for a specific number of units of blood component (or whole blood). For example, a Pall Purecell® RCEZ filter is designed for one unit of red blood cells or whole blood. When the specified quantity of the blood component is transfused, the filter needs to be changed if an additional unit is to be transfused.

The issue of length of time for a filter to remain in use should not be confused with the recommended time for completion of a transfusion.

The Circular of Information (published jointly by the American Red Cross, Council of Community Blood Centers, and the American Association of Blood Banks) indicates 4 hours as the maximum duration for an infusion16.


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Question 11: Do I still need to leukocyte reduce blood products if it has already been gamma irradiated?

Answer:
Yes. There is no indication that gamma irradiation reduces the adverse effects of leukocytes when allogeneic blood transfusions are administered.

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Question 12: Does a blood product have to be gamma irradiated if it has been leukocyte reduced with a Pall filter?

Answer:
Yes. The level of leukocyte reduction that must be achieved to protect a patient against graft verse host disease (GVHD) has not yet been identified. As such, the transfusion service/blood center should continue to gamma irradiate blood product in accordance with their requirements.

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Table 1. Blood Transfusion Filters for the Hospital Bedside/Laboratory

Product(s) Indication Performance (residual leukocytes/unit)
Red Cell
Purecell® RCEZ (gravity prime), Purecell RCQ (gravity prime/ rapid flow setting), Purecell RCXL1
Bedside filtration of one unit of packed red blood cells or whole blood Consistently averaging <2 x 105
Purecell RCXL2 Bedside filtration of two units of packed red blood cells or one unit of whole blood Consistently averaging <2 x 105
Platelet
Purecell® PXLA
Filtration of a single unit of apheresis platelets produced on systems using protocols designed to produce an initial level of leukocyte reduction Consistently averaging <3 x 104
Purecell PL6 (gravity prime) Bedside filtration of a pool of up to 6 random donor platelets or standard apheresis unit Consistently averaging <5 x 105
Purecell PXL8 Bedside filtration of a pool of 3 to 8 random donor platelets or standard apheresis unit Consistently averaging <5 x 105
Purecell PXL12 Bedside filtration of a pool of 8 to 12 random donor platelets or standard apheresis unit Consistently averaging <5 x 105
Plasma
Purecell LPS2
Filtration of up to 1600mL of fresh frozen plasma Consistently averaging <4 x 104
Microaggregate Filter
Pall SQ40S Microaggregate Blood Transfusion Filter
For the transfusion of whole blood, packed red blood cells, platelet and granulocyte concentrations and filtration of ViaSpan® Cold Storage Solution (ViaSpan is a registered trademark of DuPont Merck Pharmaceutical Co.) Not applicable
Pediatric/Neonatal Transfusion
Purecell NEO
Filtration of an aliquot of up to 60mL of packed red blood cells Consistently averaging <2 x 105
Purecell PL1 Filtration of one unit of platelet concentrate derived from a unit of whole blood Consistently averaging <4.5 x 104
Hospital Laboratory Filtration
Purecell BPF (gravity prime)
Laboratory filtration of one unit of packed red blood cells or whole blood Consistently averaging <5 x 104
Purecell LRF Laboratory filtration of a pool of up to 6 random donor platelet concentrates or standard apheresis unit Consistently averaging:
<5 x 105 (platelet pool)
<2 x 105 (standard apheresis unit)
Pall LRF10 Laboratory filtration of a pool of up to 10 random donor platelet concentrates or standard apheresis unit Consistently averaging <5 x 105


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Table 2: Considerations in Selecting Laboratory Versus Bedside Leukocyte Reduction*

Table 2: Considerations in Selecting Laboratory Versus Bedside Leukocyte Reduction*

Ease of Use

Leukocyte reduction filters are easy to use whether they are used at the bedside, in the hospital transfusion service, or in the regional blood center. For maximum ease of use, red blood cell (RBC) units that have been leukocyte-reduced in the laboratory may be preferred for specific applications such as operating room, pediatric, neonatal, outpatient, and home-care transfusions.


Quality assurance

Filtration in the laboratory provides a quality-assured product. Quality control testing may be performed ensuring that expected leukocyte residual levels are met.When bedside filters are used, inservice training should be provided for all users to ensure that filters are used correctly.


Timing

When to filter platelets: Laboratory and bedside filtration both have advantages. Laboratory filtration at the time of collection prevents the accumulation of bioreactive substances released by stored leukocytes that have been associated with patient reactions. An advantage of bedside filtration is that specific leukocyte reduction filters consistently will reduce the level of the anaphylatoxin C3a, which is associated with proinflammatory and immunomodulatory effects.

When to filter red blood cells: When RBC units are leukocyte-reduced prior to storage, a decrease occurs in the concentration of substances (e.g., serotonin, histamine, acid phosphatase, elastase) that are released by leukocytes and platelets during storage. Prestorage filtration of the red blood cell units prevents the accumulation of such potentially dangerous metabolites (Brecher, 1991) Frewin et al. (1989) suggested that the higher levels of histamine found in stored RBC units that had not been leukocyte-reduced prestorage may contribute to a higher rate of anaphylactoid reactions (rash, wheeze, flushing) in patients experiencing transfusion reactions.


Cost-effectiveness

The cost-effectiveness of bedside versus laboratory filtration depends on various factors related to the specific institution and suppliers of filters and blood components. Regional blood centers that may supply leukocyte-reduced components to the hospital or institution typically add a charge for the service provided. Off-setting this charge are savings to the hospital in filter inventory costs, staff time, and training time.


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