Blood filter and method for filtering blood

Abstract

The present invention relates to a method for filtering blood to produce plasma or serum and to a blood filter for the production of plasma or serum from a blood sample. The invention further relates to a kit comprising a blood filter for the production of plasma or serum from a blood sample and a syringe.

1 . A method for filtering blood to produce plasma or serum, comprising the steps of:
 (a) providing a blood filter comprising a filter membrane having opposite first and second sides and a receiving compartment defining a hollow space; and   (b) inserting a blood sample into said receiving compartment, wherein the volume of said hollow space is 3 to 20 times larger than the volume of said blood sample, thereby increasing the gas pressure within said receiving compartment so that said blood sample is filtered by said filter membrane, and wherein said plasma or serum comprised in said blood sample is forced through said filter membrane.   
     
     
         2 . The method of  claim 1 , wherein said blood sample is inserted into said receiving compartment via a syringe or a pipette only filled with said blood sample. 
     
     
         3 . A method for filtering blood to produce plasma or serum, comprising the steps of:
 (a) providing a blood filter comprising a filter membrane having opposite first and second sides and a receiving compartment having a first volume;   (b) inserting a blood sample and a gas into a syringe having a plunger, the blood sample occupying a second volume and the gas occupying a third volume in the syringe;   (c) connecting said syringe to said blood filter to be in fluid communication with each other; and   (d) increasing the pressure within said syringe by moving the plunger to a position such that the third volume is compressed by between 1/20 to 1/5, so that said blood sample is filtered by said filter membrane, wherein said plasma or serum comprised in said blood sample is forced through said filter membrane.   
     
     
         4 . The method of  claim 3 , further comprising the step e) of compressing the first and third volume by pressing down the plunger of said syringe beyond a position where the blood sample is received by said receiving compartment. 
     
     
         5 . The method of  claim 1 , wherein said receiving compartment has at least one opening covered with said first side of said filter membrane. 
     
     
         6 . A kit comprising a blood filter for the production of plasma or serum from a blood sample and a syringe; the blood filter comprising
 a filter membrane having opposite first and second sides;
 a receiving compartment defining a hollow space for receiving a blood sample to be filtered from said syringe, said receiving compartment having at least one opening covered with said filter membrane, wherein said first side is facing the receiving compartment, and wherein the hollow space of said receiving compartment has a first volume; and 
 a sampling compartment being arranged on said second side of said filter membrane; 
 wherein the syringe is adapted to receive a predetermined second volume of blood sample; and 
 wherein the first volume is 3 to 20 times larger than the second volume. 
   
     
     
         7 . A kit comprising a blood filter for the production of plasma or serum from a blood sample and a syringe; the blood filter comprising
 a filter membrane having opposite first and second sides;   a receiving compartment defining a hollow space for receiving a blood sample to be filtered from said syringe, said receiving compartment having at least one opening covered with said filter membrane, wherein said first side is facing the receiving compartment, and wherein the hollow space of said receiving compartment has a first volume; and   a sampling compartment being arranged on said second side of said filter membrane;   wherein the syringe is adapted to receive a predetermined second volume of blood sample and a predetermined third volume of a gas; and   wherein the syringe is adapted to compress the third volume by between 1/20 to 1/5 of the third volume.   
     
     
         8 . The method of  claim 1 , wherein the first volume of said hollow space or the sum of said first and third volume is at least 0.3 ml. 
     
     
         9 . The method of  claim 1 , wherein said receiving compartment is made from a material that is adapted to withstand an internal pressure of at least 7 kPa, preferably at least 18 kPa, more preferably at least 35 kPa without substantial deformation, preferably from a substantially inelastic and/or rigid material. 
     
     
         10 . The method of  claim 1 , wherein at least 50%, preferably at least 75%, more preferably at least 90%, and most preferably at least 95% of the surface area of the second side of said filter membrane is covered. 
     
     
         11 . The method of  claim 10 , wherein the second side of the membrane is in contact with a substantially flat substrate, wherein said flat substrate is preferably part of the sampling compartment. 
     
     
         12 . The method of  claim 1 , wherein the filter further comprises a hydrophilic and porous sheet arranged on the first side of said filter membrane in said receiving compartment which is preferably covering said filter membrane, wherein said porous sheet is made of fibrous material. 
     
     
         13 . The method of  claim 1 , wherein said receiving compartment comprises a sample insertion means, which is a one-way-valve. 
     
     
         14 . The method of  claim 1 , wherein said sampling compartment comprises an outlet. 
     
     
         15 . The kit of  claim 7 , wherein the syringe comprises a plunger and a first stop for the plunger of the syringe to stop the plunger during suction or pulling. 
     
     
         16 . The kit of  claim 15 , wherein the syringe comprises a second stop for the plunger of the syringe to stop the plunger during pushing downwards in order to limit the compression of the third volume. 
     
     
         17 . The kit of  claim 16 , wherein the first and second stops are arranged such that the third volume is compressed by between 1/20 to 1/5 of the third volume. 
     
     
         18 . The kit of  claim 6 , wherein the syringe comprises means to arrest the plunger thereof in a predetermined position. 
     
     
         19 . A method of filtering blood to produce serum or plasma comprising using the kit of  claim 6 . 
     
     
         20 . A blood filter for the production of plasma or serum from a blood sample, comprising:
 a filter membrane having opposite first and second sides;   a receiving compartment defining a hollow space for receiving a blood sample to be filtered, said receiving compartment being arranged on said first side of the filter membrane, the filter membrane resting on a seating, wherein at least 50% of the surface of the second side of the filter membrane is in contact with said seating, and wherein the seating comprises a plurality of channels for collecting the filtered blood sample.   
     
     
         21 . The filter of  claim 20 , wherein the seating is convex having a radius of curvature between 30 and 150 mm. 
     
     
         22 . The filter of  claim 20 , wherein at least 75%, of the surface of the second side of the filter membrane is in contact with said seating. 
     
     
         23 . The filter of  claim 20 , wherein the plurality of channels cover between 0.5 and 15% of the surface of the seating. 
     
     
         24 . The filter of  claim 20 , wherein the plurality of channels forms a sampling compartment having a volume in the range between 0.06 mm 3  and 3.5 mm 3 , per cm 2  of the filter surface. 
     
     
         25 . The kit of  claim 6 , wherein the first volume of said hollow space or the sum of said first and third volume is at least 0.3 ml. 
     
     
         26 . The kit of  claim 6 , wherein said receiving compartment is made from a material that is adapted to withstand an internal pressure of at least 7 kPa, preferably at least 18 kPa, more preferably at least 35 kPa without substantial deformation, preferably from a substantially inelastic and/or rigid material. 
     
     
         27 . The kit of  claim 6 , wherein at least 50%, preferably at least 75%, more preferably at least 90%, and most preferably at least 95% of the surface area of the second side of said filter membrane is covered. 
     
     
         28 . The kit of  claim 27 , wherein the second side of the membrane is in contact with a substantially flat substrate, wherein said flat substrate is preferably part of the sampling compartment. 
     
     
         29 . The kit of  claim 6 , wherein the filter further comprises a hydrophilic and porous sheet arranged on the first side of said filter membrane in said receiving compartment which is preferably covering said filter membrane, wherein said porous sheet is made of fibrous material. 
     
     
         30 . The kit of  claim 6 , wherein said receiving compartment comprises a sample insertion means, which is a one-way-valve. 
     
     
         31 . The kit of  claim 6 , wherein said sampling compartment comprises an outlet. 
     
     
         32 . The kit of  claim 31 , wherein the outlet comprises a universal adaptor.