Serum Separator Type Container

Abstract

Following mechanical or chemical separation of serum or plasma from the formed elements of blood, the serum or plasma is physically isolated from the precipitated formed elements by inserting a plug into the collection tube. The plug consists of a fibrous filter disc fastened to a rubber member having perforations which open when the pressure underneath the plug is greater than the pressure above the plug, but which are otherwise closed. A handle for manipulating the plug functions as a container to collect and remove serum or plasma. In an alternative embodiment, the handle is removably attached to the plug so that the plug can be left in place in the collection tube, maintaining isolation between the serum and the formed elements. In another alternative, the plug is provided with a container for collecting and storing serum. A similar plug inside the container is used to effect an additional filtration step.

Description

BACKGROUND OF THE INVENTION

This invention relates to blood analysis, and particularly to an apparatus and method for maintaining isolation between the formed elements of blood and the serum or plasma after mechanical or chemical precipitation of the formed elements has taken place.

Ordinarily, separation of the formed elements (white cells, red cells and platelets) of blood from the serum is accomplished by the use of a centrifuge. In my copending application, Ser. No. 847,469, filed Aug. 4, 1969, there is described a method of chemically separating serum or plasma from the formed elements of blood by adding a positively charged polymer and a lectin to the blood in a collection tube.

With either method, a short time after the formed elements are precipitated, the red blood cells begin to liberate potassium and other contaminants which may interfere with the tests performed on the serum or plasma. Consequently, it is desirable to isolate the serum or plasma from the formed elements promptly after mechanical or chemical precipitation. With chemical separation methods, small amounts of red cells and fibrin may be left in suspension, and it therefore is also desirable in the case of chemical separation to remove all of the residual suspended matter from the serum or plasma.

In the past, attempts have been made to isolate centrifugally separated serum from the formed elements by the use of a pick-up device consisting of a first tube fitted at the lower end with a rubber element adapted to engage and slide along the walls of a collection tube. The pick-up device has a second tube which passes through an opening in the rubber element to a point near the upper end of the first tube, and the second tube has a downwardly facing opening which delivers serum into the first tube as the pick-up device is pushed into the collection tube. The device is inserted into the collection tube, fills with serum, and is then removed from the collection tube. The serum retained in the device can then be tested.

A problem with the use of the device just described is that it cannot be used to transport the separated serum or plasma to the laboratory for testing from the point at which the blood sample is taken. Consequently, the collected serum must be transferred to a suitable container in a time-consuming and error-prone procedure. This problem becomes serious where blood tests are being performed for a large number of persons.

If the pick-up device just described were used in conjunction with a chemical separation method where the presence of suspended debris in the serum or plasma is likely, the debris would pass into the first tube of the pick-up device through the second tube.

SUMMARY OF THE INVENTION

In accordance with this invention, the serum separator includes a plug consisting of a disc having one-way valve openings associated with a fibrous filter disc which prevents suspended debris and formed elements from passing through the plug. The plug thus maintains the separated serum or plasma relatively free of contaminants.

In accordance with a first embodiment of the invention, there is provided a separation device which, itself, may be used for transporting serum or plasma to the laboratory for testing.

In accordance with a second embodiment of the invention, a separation plug is left in the blood collection tube, and maintains the formed elements and the serum or plasma isolated from each other. In this case, the collection tube itself can be used for transporting the serum or plasma to the laboratory.

In accordance with a third embodiment of the invention, a separation plug is provided with a container for collecting serum or plasma. The container has its own internal separation plug similar to the one to which it is attached. The internal separation plug is used to effect a second filtration prior to testing of the serum or plasma.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical section of a blood collection tube showing a first embodiment of the serum separator as it is being inserted into the collection tube;

FIG. 2 is a top plan view of the plug at the lower end of the serum separator shown in FIG. 1;

FIG. 3 is a bottom plan view of the plug at the lower end of the serum separator shown in FIG. 1;

FIG. 4 is a vertical section taken on the plane indicated at 4--4 in FIG. 2;

FIG. 5 is a vertical section of the closure shown at the upper end of the serum separator in FIG. 1;

FIG. 6 is a sectional view showing, in detail, a perforation in the plug of FIG. 4 in the condition which exists when the serum separator is being inserted into the collection tube;

FIG. 7 is an exploded view of a second embodiment of the invention, showing a removable handle, a perforated plug, and a fibrous filter disc in a separated condition;

FIG. 8 is an elevation of a blood collection tube showing the perforated plug and fibrous filter disc in place maintaining separation between formed elements in the lower part of the collection tube and serum or plasma in the upper part of the collection tube;

FIG. 9 is a vertical section of a blood collection tube showing the third embodiment of the invention; and

FIG. 10 is a top plan view of the serum container of the third embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The first embodiment of the invention, by which serum or plasma is removed from the collection tube in a separate container, is illustrated in FIGS. 1 through 6.

The collection tube 10 is preferably a tube of a well-known type used for drawing blood from a patient's vein by means of a vacuum. A serum separator 12 is shown partially inserted into tube 10. Separator 12 consists of a tube 14, sufficiently long that, when the lower end is near the bottom of collection tube 10, its upper end protrudes beyond the opening at the upper end 16 of the collection tube.

A plug 18 is fitted into the opening at the lower end of the separator tube 14, the fit being sufficiently tight that the plug will not pull out of the separator tube in normal usage. Retaining means such as inwardly extending ridges (not shown) in the collection tube may be provided if desired, but are not necessary.

The details of plug 18 are illustrated in FIGS. 2, 3 and 4. The plug comprises a disc 20 and an integral upstanding short tube 22, both preferably consisting of rubber or a synthetic polymer such as polyvinylchloride. Various other resilient materials may be used so long as they exhibit sufficient resiliency to provide an adequate seal between the edge 24 of the disc and the collection tube and to allow the one-way valves 26 to operate properly.

Valves 26, as shown in FIG. 6, consist of flaps 28 formed in the rubber and adapted to close off holes 30 which extend part way through the rubber disc. The valves may be formed in the rubber disc by first producing holes 30, and then producing V-shaped slits (FIG. 2) from the top of the disc, which meet the upper ends of the holes 30.

The upstanding tube 22 fits into the lower end of separator tube 14. Edge 24 is tapered to allow the plug to deform easily as it is moved into the collection tube.

At the upper end of the separator tube 14, there is provided a closure 32, also preferably made of rubber or a synthetic polymer. Closure 32 consists of a disc 34 having an integral tube 36 extending into the upper end of separator tube 14. Closure 32, as shown in FIG. 5, has one-way valves 38 which are similar to those in plug 18.

Underneath plug 18, there is fastened a disc 40. Disc 40 preferably consists of compacted polypropylene fibers, but may also be made up of fibers of other polyolefins or fibers of other substances which do not react with blood. The disc 40 is adhered to the underside of rubber member 20 by a suitable cement, and is arranged with respect to holes 30 so that all fluid which passes upwardly through holes 30 must have first passed through the filter disc.

In operation of the device just described, blood is first collected in tube 10 by a conventional collection method. Following collection, the formed elements are precipitated either mechanically by the use of a centrifuge, or chemically by the addition of chemical substances. With a centrifuge, Fibrin is separated out with the formed elements, leaving serum. With chemical separation, ordinarily only the formed elements will separate out, leaving plasma rather than serum. This may be satisfactory, but if it is desired to obtain serum, a suitable clotting agent such as thrombin may be used to precipitate out Fibrin so that serum rather than plasma is left over.

After the formed elements are precipitated so that they collect at the bottom of the collection tube 10 at 42, the separator 12 is inserted into the collection tube as shown in FIG. 1. The serum or plasma 44 passes through filter disc 40, and through the one-way valves 26 into the interior of tube 14. The air which is displaced passes through one-way valves 38 in closure 32. The separator is moved downwardly to a point just above the interface between the formed elements and the serum or plasma, and is then withdrawn from the collection tube. As the separator is withdrawn, air is drawn between edge 24 of the plug and the wall of the collection tube into the lower part of the collection tube. The serum or plasma within tube 14 cannot pass through valves 26 in the opposite direction, and consequently remains within the separation tube. The separation tube itself may then be marked for identification and sent to the laboratory for testing. The separator 12 is suitable for shipping in styrofoam containers.

An alternative device is shown in FIG. 7, which is an exploded view. A plug comprises a resilient element 46 and a fibrous filter disc 48. Element 46 and disc 48 are normally cemented together. Element 46 is made of resilient rubber or rubber-like materials such as polyvinyl-chloride, and disc 48 is made from olefin fibers or other fibers such as nylon, which do not react with blood. Disc 46 has one-way valves 50 which are identical to the one-way valves shown in FIG. 6. These valves are so arranged in element 46 that any blood which passes through them must first have passed through disc 48.

Retainers 52 are attached to the top surface 54 of element 46. The retainers have overhanging parts 56 which are adapted to receive tabs 58 attached at the lower end of a tubular plastic or paper handle 60. Handle 60 is attached to the plug consisting of element 46 and disc 48 by twisting the tube 60 in a clockwise direction (looking downwardly) so that tabs 58 are held between overhanging parts 56 of retainers 52 and the surface 54. The entire assembly in FIG. 7 can then be inserted into a collection tube 62 (FIG. 8) in which formed elements have been precipitated out of serum or plasma, and the tube 62 can be detached from the plug by counterclockwise rotation when the plug is in place as shown in FIG. 8. The collection tube 62 can then be capped and sent to the laboratory for testing of the serum or plasma 64. The serum or plasma remains isolated from the formed elements 66 at the bottom of the tube by the plug; the one-way valves 50 remain closed, and the potassium which is liberated by the red cells cannot contaminate the serum or plasma 64.

FIG. 9 shows a collection tube 66, in which there is located a separation plug 68 consisting of a rubber disc 70 attached to a fibrous filter disc 72. Disc 70 has one-way valves 74 similar to those previously described. It is also provided with an integral upstanding short tube 76 having an outwardly extending lip 78 attached to engage the inwardly extending lip 80 of container 82 to provide a secure and liquid-tight seal with inwardly extending lip 80 fitting tightly into the groove 84 between lip 78 and the upper part of disc 70. Container 82 has a cylindrical inner wall 86, and a top closure 88 having a relatively narrow central opening 90. Top closure 88, as more clearly shown in FIG. 10, has retainers 92 similar to those indicated at 52 in FIG. 7. These retainers are adapted to engage tabs 94 on a handle 96 which is similar to handle 60 in FIG. 7. Handle 96 is detachable from container 82 by virtue of the removable engagement of tabs 94 underneath the overhanging parts of retainers 92.

Within container 82 there is provided a second plug 98 consisting of a rubber element 100 attached to a fibrous filter disc 102 similar to disc 72. Element 100 has a pair of ridges 101 and 103 which are in sealing engagement with wall 86, but which allow relatively easy axial sliding of plug 98 within container 82, so that the pressure required to cause the plug to slide is less than that required to open the one-way valves. Disc 100 is also provided with openings in the form of one-way valves, which permit flow of liquid upwardly through the plug as it is moved downwardly within container 82. One such opening is shown at 105. These one-way valves, like the one-way valves in the other embodiments are arranged so that any liquid which flows through the one-way valves must first have passed through the fibrous filter disc.

A mark 104 is provided on the outer surface of container 82 for the purpose of indicating that a particular volume of serum or plasma has been collected when a predetermined one of the ridges, for example ridge 101, comes into register with the mark.

In operation, the container 82 is first attached to handle 96, and plug 98 is in the lowermost possible position within container 82. The assembly is pushed downwardly into the collection tube 66, as shown in FIG. 9. As the plasma or serum 106 passes through one-way valve openings 74, it begins to fill space 108 underneath plug 98 and within container 82. Plug 98 moves upwardly with respect to container 82 as the container is pushed downwardly into collection tube 66. When ridge 101 comes in to register with mark 104, the assembly is pulled out of the collection tube, handle 96 is removed, and the container 82, now containing serum, can be packed in a styrofoam container, for example, and shipped to the laboratory for testing. At the laboratory, plasma or serum 108 in container 82 can be subjected to a second filtration to remove any residual debris by pushing plug 98 downwardly with a suitable implement inserted through opening 90. The serum or plasma, now above plug 98, can be poured through opening 90 into any suitable container for testing.

Various modifications can be made to the three embodiments disclosed. The valves in the plugs, for example, can take various forms and need not consist of holes communicating with V-shaped slits. Any similar valve which opens under the influence of a differential pressure may be used. Valves which permit flow in one direction, but which prohibit flow in the other direction are not absolutely necessary for the operation of the invention. In the embodiment shown in FIG. 1, for example, even if the valves in plug 18 were not one-way valves, the one-way valves in closure 32 would prevent serum or plasma from escaping from the separator tube 14 when it is withdrawn. A closure having no valves at all could be substituted for the closure 32, but it would have to be removed when the separator is inserted into the collection tube. Various other modifications to the invention can be made. The valves may be used in any number or placed in any position along the separator to assure its proper functioning. One or more check valves can be located at edge 24 of plug 18 to further facilitate the flow of air into the lower part of the collection tube when the serum separator 12 is withdrawn. Valves 25 inverted from the orientation shown in FIG. 4 are suitable.

Claims

I claim:

1. A serum separator suitable to remove serum from a collection tube of height sufficient to contain a quantity of serum which has been separated from the formed elements of the blood and wherein the formed elements of the blood precipitate at the bottom of the collection tube and the serum positions above the formed blood elements, the combination of

A. separator means which are insertable into and removable from the said collection tube,

1. said separator means having a height greater than the height of the collection tube and terminating in a first end and a second end,

2. said separator means including means to telescope the separator means into the collection tube to receive serum and out of the collection tube to remove serum,

3. said separator means including a serum receiving elongate, interior space;

B. plug means closing the said first end of the separator means,

1. a portion of said plug means extending peripherally outwardly from the separator means a distance sufficient to contact the collection tube in a sliding, liquid-tight junction,

2. said plug means including one-way fluid valve means,

a. said one way fluid valve means opening into the separator interior space to permit passage of serum from the collection tube into the interior space,

b. said one way fluid valve means preventing serum from exiting the interior space at the said first end; and

C. closure means closing the said second end of the separator means,

1. said closure means including one way air valve means,

a. said one way air valve means opening in a direction away from the separator interior space to permit the passage of air from the interior space when serum enters the interior space,

2.

2. the said separator means, the said plug means and said closure means cooperating to form a serum shipping container,

a. said shipping container being removable from the collection tube,

b. said serum shipping container retaining the serum therein after removal from the collection tube whereby the serum may be transported to another

location. 2. The invention of claim 1 and filtering means covering a portion of the plug means, said filtering means being positioned to filter the serum before it enters the interior space through the one way fluid valve means.

3. The invention of claim 2 wherein the one way fluid valve means and the one way air valve means each include a disc of material resistant to the passage of fluid and air, a hole penetrating a portion of the disc and terminating within the disc in a resilient flap, said flap opening in a direction away from the hole to permit the passage of fluid or air through the disc and closing in a direction towards the hole to prevent the passage of fluid or air through the disc in said direction.

4. In a combination serum collection tube and serum shipping container within which the formed elements of blood precipitate at the bottom and serum positions above the formed blood elements, the combination of

A. a hollow cylindrical tube having an open top and a closed bottom,

1. said tube containing the formed elements of blood and serum therein,

B. plug means having a bottom and a top,

1. said plug means being insertable into the open top of the tube and forming a sliding, liquid-tight seal therewith,

2. said plug means including one way fluid valve means opening in a direction away from the formed elements of the blood,

a. said valve means permitting passage of the serum as the plug means insert into the tube;

C. an operating handle associated with the plug means and having separable means to push the plug means into the open top of the tube,

1. said handle serving to push the plug means into the hollow tube through the serum toward the formed blood elements,

2. said handle disconnecting from the plug means at the separable means when the plug means are positioned within the hollow tube; and

D. a cap closing the open top of the tube after disconnecting the said handle,

1. said cap sealing the serum within the tube between the plug means and the cap to permit the tube to be employed as a shipping container.

5. The invention of claim 4 wherein the plug means are provided with retainers rising from the top, the retainers including separable handle engaging means.

6. The invention of claim 4 and filtering means covering a portion of the plug means, said filtering means being positioned to filter the serum as it passes through the one way fluid valve means.

7. The invention of claim 6 wherein the one way fluid valve means include a disc of material resistant to the passage of fluid, said disc being partially pierced by a hole which penetrates the disc from the bottom thereof, said hole penetrating a portion of the disc and terminating upwardly within the disc in a resilient flap, said flap opening in a direction away from the hole to permit the passage of fluid through the disc and closing in a direction towards the hole to prevent the passage of fluid through the disc from top to bottom.

8. In a serum collection and shipping system for use in conjunction with a collection tube wherein the formed elements of blood precipitate at the bottom of the tube and the serum positions above the formed elements of the blood, the combination of

A. a serum container slidable within the collection tube,

1. said serum container being provided at the bottom thereof with first plug means and at the top thereof with handle attaching means,

2. said first plug means including one way fluid valve means which open in a direction from the bottom to the top,

a. said first plug means admitting serum into the serum container as the serum container slides downwardly into the collection tube;

B. second plug means slidable within the serum container,

1. said second plug means having a peripheral ridge in sealing, sliding engagement with the serum container,

a. said second plug means offering less resistance to sliding forces than the said first plug means,

2. said second plug means including one way valve means opening in a direction towards the top of the serum container; and

C. a handle removably connected to the serum container at the handle attaching means thereof,

1. said handle serving to insert the serum container into the collection tube,

a. said serum entering the serum container as the serum container is pushed into the collection tube,

b. said serum sliding the second plug means upwardly within the serum container,

c. said serum being retained within the serum container by the first plug means and the second plug means,

2. said handle serving to remove the serum container and serum from the collection tube,

3. said handle being removed from the serum container after the serum container has been pulled from the collection tube to permit the serum container to be employed as a shipping container.

9. The invention of claim 8 wherein the serum container is provided with fill indication mark, the said peripheral ridge of the second plug means registering with the fill indication mark when sufficient serum has passed into the serum container.

10. The invention of claim 1 wherein the portion of the plug means extending peripherally outwardly from the separator means is fabricated of resilient material.

11. The invention of claim 8 wherein the first and second plug means are equipped with filtering means, said filtering means being positioned to filter the serum as it passes through the one way valve means.

12. The invention of claim 8 wherein the handle contacts the handle attaching means near the outer periphery thereof, said handle applying forces peripherally to the handle attaching means.

13. The invention of claim 1 wherein portion of the plug means extending peripherally outwardly from the separator is equipped with reverse valve means, said reverse valve means opening in a direction opposite to the direction of opening of said one way valve means.