RU2785280C2 - Improved filter node for whole blood and blood derivatives - Google Patents

Abstract

FIELD: medicine.

SUBSTANCE: invention relates to the field of medicine; it can be used for separation of blood into its components. A filter node for blood and blood derivatives contains case (1) defined with two semi-shells (2, 3) of thermoplastic polymer material, obtained by injection molding, between which there is cavity (4) containing filtering element (5) having two opposite flat face sides (5A, 5B), inlet (9), and outlet (13) made in opposite outer surfaces (2K, 3K) of specified case (1), communicating with specified cavity (4). Each of specified semi-shells (2, 3) contains protruding flange (30) located along a perimeter. Flanges (30) of overlapping semi-shells, in a direct contact, are welded together along one welding line for defining flange (40) of the case of the filter node and connecting two semi-shells (2, 3) together. In this case, filtering element (5) is fully contained inside cavity (4) of such a case (1) and is compressed with shelves (55) protruding into cavity (4) from each semi-shell (2, 3) at least near edges of the filtering element along its perimeter (70) and providing compression on two opposite face sides (5A, 5B) of filtering element (5). Specified shelves (55) retain filtering element (5) in a stable position inside cavity (4), and the specified thermoplastic polymer material is pliable and semi-rigid and has Shore A hardness within a range from 85 to 95.

EFFECT: invention provides retention of a filter element inside a case of a filter node in a stable composition, as well as an increase in the efficiency of filtration.

8 cl, 7 dwg, 3 tbl

Description

An object of the present invention is a filter assembly for whole blood and blood derivatives according to the characterizing part of the independent claim.

The use of filter assemblies in both laboratories and hospitals to separate a patient's blood into its components is known. Each filter assembly in particular comprises a housing of flexible polymeric material, said housing is usually obtained by joining together two sheaths surrounding an internal cavity of the housing, in which is located the means or element of the filter, for example, an element suitable for filtering leukocytes present in the blood. The housing contains an inlet and an outlet to allow blood to be filtered to enter and leave the filter assembly. The shells are joined together along the edges of their perimeters.

During the separation of blood derivatives, each node is then centrifuged to form a part along with a bag of whole blood and with various bags for collecting blood derivatives in a sterile set forming a closed circuit.

Filters made of rigid material (PVC, acrylic or others) that are centrifuged, sometimes at high speed, may crack or break due to the impacts generated in the centrifuge rotor.

In addition, collisions with other components of the kit can cause them to rupture, with obvious consequences for the possible subsequent use of the centrifuge due to loss and change in blood content (contamination or both).

US2001/0037978 describes a filter for filtering fluids such as whole blood and blood derivatives comprising first and second containment shells formed from a flexible thermoplastic polymer material such as PVC by molding processes. When such material is used, the filter assembly or filter may collapse and expand in response to the presence of an incompressible fluid (eg, fluid such as blood) or a combination of fluids (eg, air and blood) within it; as the liquid volume drops, the filter assembly collapses on its own, reducing its internal volume, preventing foaming from occurring. This makes it possible to overcome the disadvantage that arises for a rigid and inflexible filter assembly, where the simultaneous passage of air and liquid leads to said foaming.

US2001/0037978 describes prior art where filters are made using rigid plastics such as acrylic or polypropylene.

The previous document also describes the prior art, including filters constructed from one or more flexible PVC sheets, which, however, have the disadvantage that it is difficult to design openings for a tight connection between the filter and normal fluid inlet and outlet tubes (for example, blood) to be filtered into and out of such a filter.

US2001/0037978 describes a filter with apertures made integrally with the filter shells themselves. In addition, this filter ensures that the inner element or filter membrane ends at the perimeter edges of the shells and is held in a stable position in the filter housing, whereby the edges of the two shells are joined (usually by localized heat welding or ultrasonic welding). However, this solution has the disadvantage that the filter or filter element can be deformed near the edges of the cavity of the filter assembly, which impairs the optimal use of its filtering action.

US2006/0049097 relates to a filter, in particular for separating leukocytes from other blood components, containing an outer shell or housing and containing at least one intermediate layer that is part of the frame or forms a frame, having an inlet chamber that is located in a message with the input for the medium to be filtered and an output chamber that communicates with the output for the filtrate. These chambers are separated by a filter material.

The outer casing or shell is made from a flexible material such as PVC. The outer casing is welded to the intermediate layer.

The filter material is pressed together and welded to the outer casing or sheath and to the intermediate layer. This is done by a first weld inside the filter and a second weld joining the two shells defining the outer shell at the free edge of the latter.

The filter material is present between the two welds so as not to create empty spaces at the entrance to the filter media inside the filter.

WO01/91880 describes a blood collection system comprising a blood container and a filter in communication with the container, positioned to facilitate handling as a unit. The filter contains two flexible shells of medical grade plastic material that contain the filter media.

The shells are joined together by two successive concentric welds and this creates a soft cushion at the filter periphery around the filter 20 which provides improved protection against possible damage during filter manipulation between the above system and the tubes and other containers used in such a system, when the latter is moved as a whole, for example during the normal centrifugation operations to which it is subjected.

US2010/0108596 also refers to a filter assembly or filter capable of selectively removing specific substances (such as white blood cells, pathogens, proteins) from a fluid such as blood or blood derivatives. The assembly or filter is flexible and comprises two flexible sheets welded together at their peripheral edges, between which the filter material is placed.

US2007/0199897 describes a method for filtering blood and blood components and a filter device comprising a container which is preferably made from flexible synthetic resin sheet materials such as PVC, polyurethane or other thermoplastic elastomers. This filter device contains a filter material to remove substances from the blood, such as leukocytes, at a specific thickness and at areas of the filter that generate a pressure drop in the filter device. The filter material is housed in a container having a flat configuration, provided with a blood (or blood derivative) inlet for filtration and a filtered blood outlet. The container can have any shape (polygonal, curved) and it matches the shape of the filter material. A housing is also provided which contains and defines the container from the outside.

EP3053610 describes a blood treatment filter comprising a flexible container on the inlet side and a flexible container on the outlet side, said containers blocking the filter element, inlet and outlet like a sandwich. The filter assembly also comprises: a housing providing a fluid path, a first sealed portion and a second sealed portion, wherein said housing providing the fluid path comprises a pair of opposing ribs. The outlet is located between the specified ribs. This housing, providing a path for the fluid, contains a gap obtained with a pair of ribs and diffusion holes located outside the pair of ribs, which are open continuously towards the lateral parts of the first sealed part.

This prior art document begins with the prior art defined with filter assemblies containing a rigid container; however, such a container is known to damage components of a centrifuge used to separate blood constituents and, in particular, leukocytes.

For this reason, EP3053610 describes the use of a flexible container to construct such a filter assembly. However, such a solution reportedly tends to cause the container to swell and/or collapse during the process of separating the blood into its components. For this reason, first of all, in order to prevent the container from collapsing on the inner filter member, a flow ensuring device inside the container (flow path sheet) is provided.

EP3053612 relates to a blood treatment filter assembly to remove unwanted components from blood or blood derivatives; the filter comprises: a filter element in the form of a sheet and a container containing a container element or component on the input side and a container element or component on the output side, located so as to tightly hold the filter element between them. Inside the container, the space is divided by the filter element into an input space and an output space. The filter element comprises a filter surface on the input space side, a filter surface on the output space side, and an edge surface along the periphery of said filter surfaces. The container element on the inlet side and the container element on the outlet side are provided with a clamping element (clamp) which seals and compresses part of the outer edge of the pair of filter surfaces of the filter element. The clip is glued to the extreme surface with molten resin.

This prior art document describes the use of inlet side and outlet side container elements, which may be made of flexible resin, so as to form a flexible container.

Alternatively, EP3053612 describes that the material of the container may be a rigid material.

However, EP3053612 does not describe that the container may be composed of a semi-rigid and pliable material. For this reason, the known solution has the following disadvantages: if the container is made of a flexible material, it may swell or collapse on the filter element when subjected to pressure changes when blood is processed therein. If, instead, the container is made of a rigid material, it may damage the components of the centrifuge that houses the container for separating whole blood into blood components.

In addition, the container does not have two parts welded together, but the container is obtained by molding its parts into mold halves which, when closed, allow the finished container to be formed. One of these parts is formed on the filter element. A clip inserted into a closed mold to form a container with an inserted filter element makes it possible to connect the parts of the container and the filter elements together.

There is no provision for welding of the parts of the container, but instead for injection of a clamp as necessary means for connecting said parts.

Nothing is said about the packing factor of the filter assembly.

US5688460 describes a process for producing hermetically sealed filter assemblies and the product obtained therefrom. The method includes aligning a porous filter element between two shell parts and a thermoplastic edge (skirt) that overlaps the edge of at least one shell part to protect the edge of the filter element located adjacent to said edge or skirt, applying pressure to the two shell parts, and then injection molding an overlying strip of thermoplastic material around the outer portions of the sheath members to form an airtight seal at the edge of the filter element.

The invention of the prior art solves the problem of eliminating the phenomenon of jets of thermoplastic material in the filter assembly during molding.

There is no provision for welding around the perimeter between the two parts of the specified assembly.

The aim of the present invention is to provide a filter assembly for blood and blood derivatives which is improved over known assemblies.

In particular, it is an object of the present invention to provide a filter assembly in which the housing is made such that it cannot destroy the components inside the centrifuge in which it is placed when whole blood is separated into blood components.

Another object is to provide a filter assembly having an internal high efficiency filter element throughout its body.

Another goal is to provide a filter assembly that is soft to the touch and easy to handle.

Another object is to provide a filter assembly in which the filter element is held stably in position and flattened within the cavity of said assembly without being subjected to the heat generating treatment used to connect the sheaths of said assembly, as occurs in prior art solutions discussed above, where the filter element welded to the body of the filter assembly.

Another object is to provide a filter assembly of the type discussed, in which the shells can be joined together efficiently and permanently.

Another goal is to provide a filter assembly that has a high filtering efficiency.

These and other objectives, which will be apparent to those skilled in the art, are achieved with a filter assembly according to the appended claims.

Filter assembly for blood and blood derivatives, containing a housing (1) defined by two injection-molded half-shells (2, 3) made of thermoplastic polymer material, between said half-shells (2, 3) there is a cavity (4) containing a filter element (5) , having two opposite flat front sides (5A, 5B), an inlet (9) and an outlet (13) made in opposite outer surfaces (2K, 3K) of said body (1) communicating with said cavity (4),

in which each of the specified half-shells (2, 3) contains a protruding flange (30) located along the perimeter, the flanges (30) of the overlapping half-shells are welded together in direct contact along one welding line to define the flange (40) of the filter assembly housing and connect the two half-shells ( 2, 3) together, and the filter element (5) is completely contained inside the cavity (4) of such a housing (1) and is compressed by shelves (55) protruding into such a cavity (4) from each half-shell (2, 3), at least , near the edges of the filter element along its perimeter (70) and providing compression on two opposite front sides (5A, 5B) of the filter element (5), these shelves (55) hold the specified filter element (5) in a stable position inside the cavity (4) , said thermoplastic polymer material is malleable and semi-rigid, the thermoplastic polymer material has a Shore A hardness between 85 and 95.

Preferably the filter assembly has a packing ratio greater than 110%.

Preferably a filter assembly in which the flange (30) of the two half shells (2, 3) and hence the flange (40) of the housing (1) of the filter assembly protrudes 2-5 mm along the edges of such a housing.

Preferably, the filter assembly, wherein said flange (40) of the housing (1) of the filter assembly has a thickness that decreases outward or away from said housing.

Preferably a filter assembly in which said shelves (55) are alternately continuous or discontinuous and define a continuous or discontinuous ring near the edges of such half-shells (2, 3).

Preferably a filter assembly in which the edge (70) of the filter element (5) is thin compared to the rest of said filter element.

Desirably, a filter assembly in which said half-shells (2, 3) have a front side (2W, 3W) facing the cavity (4) of said filter assembly body (1), from which ribs (20) protrude, which can press against each other. opposite faces (5A, 5B) of the filter element (5), said ribs (20) define channels (21) between them in order to ensure the movement of blood and blood derivatives from the inlet (9) located in the protrusion (8) , up to the outlet (13) located in the ledge (12) of the specified housing (1) of the filter assembly.

Preferably a filter in which said inlet (9) and said outlet (13) are provided in protrusions (8, 12) protruding from the faces (2K, 3K) of said half-shells forming the outer faces of the body (1) of the filter unit, said protrusions (8, 12) are integral with said half-shells.

For a better understanding of the present invention, the following drawings are attached, for purposes of illustration only and not limitation, and therein:

Figure 1 and Figure 2 show perspective views from various angles of the filter assembly obtained according to the present invention;

Figure 3 shows a sectional view along line 3-3 in Figure 2;

Figure 4 shows a side view of the filter assembly in Figure 1;

Figure 5 shows a top view of the filter assembly from the side opposite that shown in Figures 1 and 2;

Figure 6 shows a side view of the filter assembly component in Figures 1 and 2; and

Figure 7 shows a top view of the component shown in Figure 6, the side of this component shown in Figure 7 is inside the filter assembly in Figures 1 and 2.

With respect to the figures discussed, here the filter assembly of the present invention comprises a housing 1 defined by two half-shells 2 and 3 connected together and delimiting a cavity or inner space 4 in which a filter element 5 is located subdividing such a cavity into two parts, a first cavity part 4A and part 4B of the second cavity. The filter element 5 is defined in a manner known per se, by means of a modular filter layer stack, which can be assembled according to the fluid to be filtered and/or the desired filtering effect.

The first half shell 2 (for example, located at the top in Figures 2 and 3) has a perforated outer ledge 8 and an opening 9. Between such a ledge 8 (as a whole with the half shell 2) there is a passage 10, which opens into the first cavity part 4A.

Similarly, the second half-shell 3 (lower in Figure 3) includes a first perforated outer projection 12 integral with the half-shell 3, an opening 13 and has a passage 14 opening into the second cavity portion 4B. The passage 16 located between the opening 17 of the second perforated outer projection 19 also opens into this part 4B of the cavity.

Shells 2 and 3 are injection molded and have corresponding projections integral with them. The first protrusion 8 can be connected to a flexible PVC, polyurethane or the like (not shown), the second protrusion 12 can also be connected to a flexible pipe. The third protrusion 19 only functions as a vent for the air present in the filter 1 when the second cavity portion 4B receives blood or blood-derived fluid from the first cavity portion 4A through the filter element.

Each half-shell 2, 3 has a first side 2K, 3K, which defines the corresponding outer face of the body 1, and a second face 2W, 3W, opposite the first, delimiting the cavity 4 (and hence the interior of the body 1). On this second front side 2W and 3W, each half-shell 2, 3 has a plurality of ribs 20 of various lengths delimiting a plurality of channels 21.

These channels 21 in the first half shell 2 cause the fluid entering the first cavity part 4A to be distributed over the entire corresponding face 5A of the filter element 5 (the face facing such cavity part 4A). In this way, fluid (for example, blood) is correctly filtered through such an element 5.

Likewise, the channels 20 in the second half-shell 3 direct such filterable fluid present in the second cavity portion 4B towards the protrusion 12 from where it is removed. The filter element 5 and its opposite faces 5A, 5B are also supported on these ribs 20; the ribs provide planarity and rigidity for such a filter element 5, which is most important to obtain the correct distribution of the blood fluid, in addition to the presence of the correct retention factor for the filter element, which is necessary to ensure its optimal filtering efficiency, as will be further discussed below.

The half shells 2, 3 are made from a semi-rigid thermoplastic polymer material having a Shore A hardness between 85 and 95. A material having these characteristics will also be referred to herein as imparting semi-rigid compliance properties to the body 1. referred to as “semi-rigid and pliable”, with the characteristics to be specified below.

Suitable materials are known and are, for example, PVC, SBS, PU or the like. These half shells 2, 3 are produced by injection molding. Due to the hardness of the material from which they are produced, the half-shells 2, 3 have a soft damping effect against impacts with external components. This is particularly advantageous during washing in a centrifuge, since it prevents the components of the drawn blood and the processing system (bags, tubes, filter assemblies) present in such a centrifuge from being destroyed in case of contact with the body 1.

In addition, the (intrinsic) rigidity of the material used to make the half-shells makes it possible to adjust the density of the filter element 5 (which, as discussed, is usually determined by the plurality of filter layers). In fact, it is known that the efficiency of such an element 5 is related to its compression ratio or “packing factor”. This is provided by the ratio between the density of the compressed filter element (in the form of layers) and the density of the same filter element when it is not compressed.

When using the filter assembly 1 containing the filter element 5 with different packing ratios, changes in the filtering efficiency of the assembly 1 are actually detected, as can be seen from the table below.

Packing ratio % Leukocytes/after filter assembly Log decrease in WBC =100% 4.97E+04 four = 110% 4.37E+04 5 = 140% 3.88E+04 6.3

where

Packing ratio = compression ratio as shown above

Leukocytes/after filter node = [residual leukocytes]

Log WBC reduction = [log decrease]

From the above, it will be seen how the filtration efficiency is related to the compression ratio of the filter element: the higher this factor, the greater the filtration capacity. This means that for identical filter elements, a filter assembly in which such elements are not compressed very much will filter worse than a filter assembly in which such elements are more compressed.

By specifically choosing the hardness of the materials constituting the shells 2 and 3 of the housing 1, the present invention makes it possible to obtain a filter assembly sufficiently rigid that it can contain a filter element that is subjected to light compression, and at the same time, be rigid enough that it can adequately how to protect such an element and make it easy to manipulate. At the same time, this hardness makes it possible to obtain a filter assembly that is soft enough not to damage other filter assemblies, tubing, bags or other components of the blood collection and processing system when it, together with similar systems, is placed in a centrifuge for conventional operations to which such systems are subjected.

Three filter assemblies were prepared according to “configurations”, 1, 2 and 3 in the Table shown above, to study the filtering efficiency of the filter assembly of the present invention.

Specifically, in the first configuration (configuration 1), the filter assembly comprises a filter element 5 formed by a pack of forty PET/PBT filter layers having a theoretical thickness of each layer of 0.31 mm and a mass per unit surface area of 52 g/m ² . In the second configuration ("configuration 2") only the number of filter element layers is changed (now thirty-six), and in the third configuration ("configuration 3") the number of filter element layers is again changed to fifty.

A set of three filter assemblies is prepared for each filter media configuration. Filter assembly with PVC half-shells but with different stiffness, i.e. the first assembly containing semi-rigid half-shells according to the present invention (hardness Shore A 93±2), with soft half-shells (hardness Shore A 85±2) and with hard half-shells (hardness H358/30 95 MPa) are obtained for each configuration.

Given that filter assemblies containing rigid half-shells allow a high packing factor to be obtained (while it is possible to create high pressure on the internal filter element), when reading the table shown above, it is important to compare them with an example of a filter assembly obtained using a rigid material.

Various configurations of filter assemblies (with the filter element obtained in different ways) are used for the filtration study according to the study protocol, including the following characteristics:

WBC count/serving* 2.5-3.0⋅10 ⁹ Platelet count/serving* Depends on the centrifugation method The temperature of the blood to be filtered Between 4°C and ambient temperature Age of the portion of blood to be filtered max 10 days after receiving Hematocrit (Hct)/Serving* 0.65-0.75
Added solution
0.50-0.70 Minimum hemoglobin content /serving* 45 g Node volume* 280±ml Distance between the portion of blood to be filtered and the collection bag 180 cm Method for counting leukocytes Najotte chamber, DNA labeling or cytofluorometry Filter priming Yes

The results shown in the Table below are obtained using different nodes according to different configurations.

semi-rigid malleable Hard H
semi-rigid Filter density [g/dm3] Packing factor Semi-rigid efficiency H malleable Filter density [g/dm3] Packing factor Compliant efficiency H hard Filter density [g/dm3] Packing factor Efficiency of hard Configuration
one ten 208 124% 5LOG 12 173 103% 3.5LOG ten 208 124% 5LOG Configuration
2 ten 187 112% 4LOG ten 187 112% 4LOG ten 187 112% 4LOG Configuration
3 11.5 226 135% 6LOG fourteen 186 111% 4LOG ten 260 155% 6.5LOG

When examining what is shown in the above table, it should be noted that the filter assemblies with semi-rigid case 1 have a filter density that is comparable to the filter assemblies with a rigid case, as a result, with an equivalent or identical packing factor. Conversely, in the case of filter assemblies with soft housings, the density of the filter is lower and the packing factor is also lower.

Therefore, ongoing studies demonstrate how the present invention benefits from the fact that the filter assembly housing 1 is composed of the pliable and semi-rigid half-shells shown above, but at the same time has a packing factor of more than 110% and is in any case comparable to packing factor of known rigid filter assemblies.

Each half-shell 2, 3 has a perimeter flange 30 protruding laterally from the shell. The flanges 30 of the two half-shells 2, 3 overlap when the body 1 is formed and they form an assembly (the perimeter filter assembly body flange 40 protruding from the body 1) which is flexible (due to the material of which the half-shells are made) so that they can convenient to manipulate.

In addition, the body 1 obtained in this way remains intact during the centrifugation process due to the flexibility and impact resistance properties of the semi-rigid or soft material, while at the same time making it possible for the components of adjacent blood collection and processing systems (as shown above) not to be damaged during centrifugation.

The flanges 30 are welded together over their entire surface area along a single welding line and without any foreign component placed between them, and in particular, there is no filter element between them. Welding is usually carried out by thermal welding or using ultrasound, and due to the fact that it is carried out directly between homogeneous parts of the same material, the welding is wear resistant and remains strong over time. The welding line is preferably continuous.

The flanges 30 are made in such a way that, after welding, the thickness resulting from the fusion is between 1 and 2.5 mm, and this, in combination with a material having a hardness in the predetermined range indicated above, helps to obtain a soft flange 40, which is comfortable to use.

Such a flange 40 may also have a variable thickness decreasing in the outward direction.

The filter element 5 is held by half-shells 2 and 3, in addition to the ribs 20, and also by protruding shelves 55 located close to the edges of these half-shells on the front sides 2W and 3W of said half-shells, close to their perimeter edge. These flanges 55, which may be continuous on each face 2W or 3W or discontinuous, form some kind of (solid or discontinuous) ring that compresses the faces 5A and 5B of the filter element 5, fixing this element between the half-shells. In particular, these shelves 55 compress said filter element 5 close to its edge along the perimeter 70 of small thickness. Due to this, the modular combination of the number and type of filter layers can be changed without the negative effect of welding the flanges 30 and, as a result, overlapping the perimeter of the body 1, while the filter module does not adversely affect the welding of the half-shells, but is completely retained inside them and is compressed at its edge along perimeter, thereby obtaining a product (filter unit) having performance characteristics suitable for specific applications or for different types of blood derivatives.

As discussed, the shelves 55 span the periphery of the cavity portions 4A and 4B. This feature, together with the configuration of the ribs 20 delimiting and defining the channels 21, allows the fluid entering the filter assembly via the projection 8 to be transported in an optimal way in the direction of the filter element 5 and, after passing through it, in the direction of the projection 12. This prevents bypass filter element 5 on the edge 70 of its perimeter.

By means of the present invention, a filter assembly is obtained having the characteristics described above. However, other embodiments are possible while remaining within the scope of the present invention as defined by the following claims.

Claims (8)

1. The filter assembly for blood and blood derivatives, containing a housing (1), defined by two injection molded half-shells (2, 3) of thermoplastic polymer material, between the said half-shells (2, 3) there is a cavity (4) containing a filter element ( 5) having two opposite flat faces (5A, 5B), an inlet (9) and an outlet (13) made in opposite outer surfaces (2K, 3K) of said body (1) communicating with said cavity (4) , characterized in that each of the specified half-shells (2, 3) contains a protruding flange (30) located along the perimeter, the flanges (30) of the overlapping half-shells are welded together in direct contact along one welding line to determine the flange (40) of the filter assembly housing and connection two half-shells (2, 3) together, and the filter element (5) is completely contained inside the cavity (4) of such a housing (1) and is compressed by shelves (55) protruding into such a cavity (4) from each p shells (2, 3), at least near the edges of the filter element along its perimeter (70) and providing compression on two opposite front sides (5A, 5B) of the filter element (5), these shelves (55) hold the specified filter element ( 5) in a stable position inside the cavity (4), said thermoplastic polymer material is pliable and semi-rigid, the thermoplastic polymer material has a Shore A hardness between 85 and 95. 2. Filter assembly according to claim 1, characterized in that it has a packing factor greater than 110%. 3. The filter unit according to claim 1, characterized in that the flange (30) of the two half-shells (2, 3) and, consequently, the flange (40) of the housing (1) of the filter unit protrude by 2-5 mm along the edges of such a housing. 4. Filter assembly according to claim 3, characterized in that said flange (40) of the housing (1) of the filter assembly has a thickness that decreases outwards or away from said housing. 5. Filter unit according to claim 1, characterized in that said shelves (55) are alternately continuous or discontinuous and define a continuous or discontinuous ring near the edges of such half-shells (2, 3). 6. Filter assembly according to claim 1, characterized in that the edge (70) of the filter element (5) has a small thickness compared to the rest of said filter element. 7. The filter assembly according to claim 1, characterized in that said half-shells (2, 3) have a front side (2W, 3W) facing the cavity (4) of said housing (1) of the filter assembly, from which ribs (20) protrude ) that can press against each other the opposite faces (5A, 5B) of the filter element (5), said ribs (20) define channels (21) between them in order to ensure the movement of blood and blood derivatives from the inlet (9) located in the ledge (8) to the outlet (13) located in the ledge (12) of the specified housing (1) of the filter assembly. 8. The filter assembly according to claim 1, characterized in that said inlet (9) and said outlet (13) are provided in protrusions (8, 12) protruding from the front sides (2K, 3K) of said half-shells forming outer front sides of the body (1) of the filter assembly, said protrusions (8, 12) are integral with said half-shells.

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